The designated hitter spot presents American League teams with an opportunity that their NL brethren don’t get to take advantage of. This seems like an advantage that every team should exploit, but as we’ve seen so far in 2010, that doesn’t always happen.

Thus far this season DHs are hitting a combined .246/.336/.412 in 1,228 plate appearances, which is pretty much league average. In terms of batting average, only catchers have fared worse. The DH spot ranks fourth in OBP, behind right field, left field, and first base, and ranks fifth in slugging, behind those same positions plus center field. Shouldn’t players who have no responsibilities other than to hit perform better than their two-way counterparts? Theoretically this is the case, but in practice, a number of teams end up featuring former stars with big contracts in the DH role, because they have no other place to play them.

The A’s, Red Sox, and Indians have suffered their most from their designated “hitters.” Eric Chavez ranks the best among the three with a .236/.279/.345 line. The other two, David Ortiz and Travis Hafner, have combined for a .180/.273/.324 mark, not much better than what those teams would get if they let their pitchers hit. Normally players who produce these numbers would sit on the bench, but these three players will make a combined $36 million in 2010. While continued poor production might force Ortiz and Chavez from the lineup since their contracts expire after this season, Hafner has two years and $28.75 million left on his deal. The Indians will probably give him every chance to revert to his former self.

A few years ago, Ortiz and Hafner received big-money deals to exclusively serve as DH, but as baseball puts a greater emphasis on defense, we’ll see if players with no value in the field continued to be paid like stars. Considering Jermaine Dye hasn’t been able to find a deal to his liking, it seems unlikely.

Kosuke Fukudome wasted no time winning Cubs’ fans hearts in 2008, hitting a game-tying three-run home run in his major league debut, and blistering the baseball in his first month in the majors. At the end of his first April, he was hitting .327/.436/.480 and looked like a star.

The rest of the season didn’t go quite as well. Fukudome hit .241/.340/.355 from May through September, showing little power and earning a late season benching. In 2009 we saw much of the same. In his 89 April plate appearances Fukudome hit .338/.461/.592, an improvement even over his hot April 2008. The rest of the way he hit .245/.360/.393, again a bit better than 2008 but still a disappointment after another torrid start.

He’s again off to a good start — he’s hitting .297 — yet Cubs fans have been conditioned to expect much worse once the calendar turns to May. Why has he hit so much better in April than the rest of the year?

It is tough to assign cause to such a small sample, however, we can see a discrepancy in his batted ball types in April compared to the rest of the season. In the first month of the year, Fukudome hits the ball in the air and drives it with some regularity, as seen in the graph below. It shows the percentage of flyballs to each zone divided by total balls in play, with the colors showing slugging percentage — the redder the better. As you can see, he turns into a groundball machine as the season wears on. And after driving the ball to right field seven percent of the time in April, that number drops to three percent the rest of the year.

If you’re more of a numbers person than a graph person, Fukudome’s career GB percentage in April is 41 percent, compared with 50 percent the rest of the year.

At a glance, it might seem like hitting ground balls isn’t all a bad thing. Ground balls, after all, produce hits at a greater rate than fly balls. But that only touches on one dimension of hitting — and even then, it’s not a particularly compelling argument. Last year in the National League ground balls produced a .234 batting average, while fly balls produced a .224 average. (Line drives, the third type of batted ball, had a .728 average.) But slugging percentage on fly balls is considerably higher than on grounders. NL hitters slugged .595 on fly balls last season, while they slugged just .255 on ground balls. It’s pretty hard to hit a groundball over the wall.

While some hitters can benefit from hitting the ball on the ground, Fukudome does not profile as one of them. He possesses the power to hit near or in the middle of the order, having hit 31 homers for the Chunichi Dragons in 2006. However, he doesn’t take advantage of this power once the calendar flips to May. He’s off to a strong start again, and he has kept the ball in the air at a greater frequency than in his past two seasons. Maybe it’s Fukudome’s year, but until he shows the ability to hit fly balls and line drives in the later months, don’t expect an improvement.

When the Giants signed Barry Zito to a seven-year, $126 million contract after the 2006 season, few thought he would live up to it. He was four years removed from his stellar Cy Young season at the time, and in the ensuing years had shown signs of decline. His strikeout rate declined, his home run rate increased, and his batting average on balls in play (BABIP) returned to league average after years of falling far below it.

In 2009, however, Zito experienced a turnaround of sorts. His strikeout rate rose to 7.22 per nine innings, his highest rate since 2001. His walks also dropped back to around his career rate (3.8 per nine), as did his home runs allowed (0.8). Along with this went his ERA, 4.03, much closer to his career average than his previous two seasons. And after shutting out the Astros for six innings last night, it appears Zito has been reborn. What changed for him?

Part of it was the return of his curveball, a weapon that failed him during his first two seasons in San Francisco. Another large part of his transformation came from an increased use of his slider. Zito started employing a slider in 2005 after performing poorly in 2004. He didn’t throw it too often, never using it more than 8.5 percent of the time in 2005 or 2006. In 2009, however, he used it more than his curveball, throwing it 18.6 percent of the time against 18.2 percent with his curveball. During his 2010 debut on Tuesday night, Zito continued using his slider effectively.

Of the 90 pitches he threw, 11 were sliders, or 12.2 percent. He went to the changeup and curveball more often, though neither was as effective as the slider. Only one of the 11 sliders ended up outside the zone, and Zito generated three swings and misses off the slider, more than the changeup and curveball combined. Additionally, he threw eight of those 11 sliders in a two-strike count, signaling that it could be employed as his primary out pitch this season. In his six innings of work, the southpaw fanned six, walked one, and allowed just three hits in the Giants’ 3-0 win.

It seems that Zito learned something during his poor 2008 season, when he had a career-high 5.15 ERA. That was when he started increasing his slider usage, and it proved his most effective pitch. In 2007, he threw his slider 4.3 percent of the time. In 2008, 9.8 percent and last year 18.6 percent. In his 2010 debut he employed his curveball and changeup more frequently, but picked his spots with the slider. It worked out for him. The slider is what turned Barry Zito back into an effective pitcher.

The Indians and the Blue Jays had something in common on Opening Day. While both staffs feature a number of promising arms, each of their Opening Day starters hadn’t thrown a pitch in the majors since 2008. Jake Westbrook, understandably, struggled during his start four Cleveland. In four innings of work he threw 82 pitches and just 47 for strikes. That led to four walks. Combined with five hits, including a two-run home run by White Sox first baseman Paul Konerko, and Westbrook surrendered five runs in his return. For Shawn Marcum, however, it was a different story.

Marcum has never been an overpowering pitcher. His fastball tops out at 88 mph, and over his career he has relied on his secondary pitches to keep hitters off-balance. He features a full arsenal, including a cutter, changeup, slider, and curveball, which allows him to throw his fastball only 40 percent of the time. While his cut fastball grades well, Marcum’s favored secondary pitch is his changeup. It averages around 81 mph, giving it only five to six mph separation from his fastball, but it is his most effective weapon.

The changeup played a large part in Marcum’s Opening Day no-hit bid. He deployed it liberally, throwing it 29 times out of 92 pitches, according to Pitch F/X. While Marcum has favored the changeup in the past, he hasn’t typically thrown it this frequently, usually using it about 20 percent of the time. Then again, it was incredibly effective during this start. Only eight times did the umpire call his changeup a ball. The Rangers swung and missed at it 11 times, including four to end at-bats, accounting for two-thirds of Marcum’s strikeout total for the day.

To measure the break of a pitch, the Pitch F/X system compares it with a pitch that has no spin. If a pitch had no spin, gravity would act on it to a greater degree than it would a pitch with backspin, so a pitch with no spin would drop faster. Because of this, many pitches have a positive vertical break. This doesn’t mean that the pitch broke upward, but rather that it didn’t drop as quickly as a pitch with no spin. A fastball with 10 inches of vertical break, for instance, stayed 10 inches higher than the same pitch if it had no spin.

The effectiveness of Marcum’s change comes not from its separation from his fastball, but from its movement. His four-seam fastball has a vertical break of around 10 to 11 inches. His changeup has a vertical break of around 5 inches, so while a pitch with no spin would drop more, the changeup drops considerably more than the fastball. The movement keeps hitters off-balance, as they oftentimes think they see fastball, only to have the ball drop under their swings.

For the past seven seasons Blue Jays fans got to see Roy Halladay, perhaps the best pitcher in baseball over that span, start on Opening Day. Seeing Marcum, over a year removed from meaningful baseball, might have been a disappointment at first, but he certainly gave them something to cheer for. It was a disappointment to see Vladimir Guerrero single with one out in the seventh inning to break up the no-hit bid, and then to see Nelson Cruz hit a home run to tie a game the Jays would eventually lose. But Marcum certainly gave Jays fans something to look forward to. He, and his changeup, could lead the Jays to a few unexpected wins in the 2010 season.

It didn’t take long for criticism to rain down on the new Yankee Stadium last season. From fans pining for the mystique and aura of the old stadium, which was still standing across the street, to the pundits who claimed it more a mall than a ballpark, everyone had an opinion about what was wrong with the park. But a few games into the 2009 season, another issue emerged: Baseballs were leaving the park at an alarming rate. The effect seemed so pronounced, in fact, that commentators came up with a new name for the Stadium: Coors Field East.

Through the season’s first two months the park lived up to the moniker. The Yankees came to bat 921 times during that span and hit 45 home runs, or one every 20.5 plate appearances (PA). Opponents didn’t have quite as much success, hitting 42 home runs in 983 PA, one every 23.4 PA. That was still far ahead of the AL pace for those two months, a home run every 35.2 PA. The Yankees claimed that the new stadium’s dimenions were identical to the old (though a few sources disputed that notion). But something appeared to be a bit different at the new park.

Two months represents a small sample, especially regarding park data. Park factors are most accurate when using a three-year sample, so a two-month sample might mean nothing. To that end, the stadium experienced a statistical correction in June. While the Yankees hit home runs at a slightly less rapid pace, one every 22.3 PA, their opponents saw a precipitous drop, hitting a home run once every 41.8 PA. Opponents never got close to their early-season marks, hitting a home run every 37.7 PA from June through season’s end. The Yankees hit a home run every 24.8 PA from June through September, a bit lower than their April and May pace.

Yankees	PA	HR	PA/HR	Opp.PA	Opp.HR	Opp. PA/HR
April	298	15	19.87	311	13	23.92
May	623	30	20.77	672	29	23.17
June	490	22	22.27	502	12	41.83
July	604	24	25.17	603	16	37.69
August	539	26	20.73	517	15	34.47
Sept	623	19	32.79	603	16	37.69
Total	3177	136	23.36	3208	101	31.76

There is no doubt that the Yankees benefitted from their new park, though that appears to be by design. The lineup featured not only three lefties, but also four switch hitters. Each of those four switch hitters has displayed more power from the left side over his career, and each also exceeded his career power numbers from the left side in 2009. After losing two lefties this off-season, the Yankees added three to their starting lineup, so perhaps we will see a similar effect this season.

But despite all those home runs, Yankee Stadium actually leaned towards being a pitchers’ park, according to ESPN’s Park Factors. While it ranked first in HR factor, it ranked second to last in doubles, with only Petco Park — considered the most cavernous park in the league — more heavily suppressing doubles. But, again, all of this uses just one year’s worth of data. In order to get a better read on how the park plays we need to study it over multiple seasons. As we saw in April and May, a few months of aberrant production can skew a season’s worth of numbers.

After a year in which three of their best players missed a major chunk of the season, the Mets needed some good news to kick off 2010. They’ve gotten some in the form of the performance of their best prospect, righthander Jenrry Mejia. After striking out more than a man per inning last season as the youngest player in the Eastern League (Double-A), the 20-year-old has been the talk of camp with his electric mid-90s fastball. He’s been so good, in fact, that the club is thinking of promoting him to the big leagues as a reliever. While he might thrive in that role, it would still be a bad decision.

Manager Jerry Manuel has pondered Mejia in the bullpen because he thinks he and Francsico Rodriguez will give the team a dynamic one-two combo to finish games. The problem is that Mejia still has a lot of development left. He admits his command issues, saying that he aims for the middle of the plate and hopes for the best. His slider also needs work, though he does feature an impressive changeup. As a reliever, these secondary pitches would not get the attention they need to improve.

The Mariners and Yankees should both provide cautionary tales for the Mets. Each tried to groom a young starter with ace potential, Brandon Morrow and Joba Chamberlain respectively, in the major league bullpen. While both performed well, they have also struggled in the transition back to the rotation. The Mariners ended up trading Morrow, while the Yankees have seemingly moved Chamberlain back to the bullpen once again.

What’s so bad about the bullpen? After all, both Morrow and Chamberlain have pitched well as relievers. Their teams, though, won’t realize maximum value. Starters affect a much greater portion of a team’s innings. If a team has 1450 IP in a season, a 200-inning starter covers 13.8 percent of the total time. A reliever who throws 70 innings affects just 4.8 percent of total innings. This shows up in Wins Above Replacement (WAR), too. Last year Barry Zito, who had had a 4.03 ERA in 192 innings, was worth 2.2 WAR, while Heath Bell, the NL saves leader, was worth 2.0 WAR. And if you don’t believe WAR, look at the free agent market, where the contracts given to top-flight starters typically dwarf those given to elite relievers.

The Mets might not have as strong a bullpen this year without Mejia, but by allowing him to properly develop in the minors they could see a greater return in the future. That’s not easy to stomach for fans who want to win today, nor is it an easy decision for Jerry Manuel and Omar Minaya whose jobs might be on the line, but it is the correct one for the future of the team. Considering the Mets haven’t featured a homegrown ace since Doc Gooden, you’d think they realize it would be foolish to stunt Mejia’s growth.

The Toronto Blue Jays’ front office knew the situation when they traded Roy Halladay to the Philadelphia Phillies this winter. Staring upward at three powerhouses in the AL East, and seeing the Baltimore Orioles rapidly improving, they had to reload their farm system with young players if they wanted to avoid a perpetual spot in the cellar. Halladay presented them with the best opportunity to acquire young talent and rebuild the team. And here’s the thing: even with Doc gone, the Jays’ pitching might not be so bad in 2010.

It would seem, at face value, that losing Halladay would be devastating to the Jays’ staff, which allowed 4.76 runs per game, 11th in the AL in 2009. But even though Halladay threw 239 innings, the rest of the rotation was ravaged by injuries and there’s reason to believe the Jays have the depth and upside in their rotation to improve on last year’s performance.

Of the 12 pitchers who started games for Toronto, one was Brian Tallet, a career reliever who posted a 5.41 ERA in 25 starts. Getting him out of the rotation will surely give the club a boost. Another starter was Brett Cecil, a college closer who recently transitioned to the rotation and had a 5.30 ERA. Just 23 years old, Cecil was a first-round pick in 2006, and there’s plenty of reason to be optimistic about a guy who averaged a strikeout per inning in the minors. Add the return of Shaun Marcum, who missed all of 2009 while recovering from elbow surgery, with an improvement from Ricky Romero (the club’s 2005 first-rounder), and it’s not hard to foresee the Jays’ staff improving on its 2009 numbers.

CHONE projects the five presumed Blue Jays starters — Romero, Cecil, Marcum, Brandon Morrow (the Mariners’ 2006 first-rounder acquired in an off-season trade), and Mark Rzepczynski — to post a 4.75 ERA, not much worse than the 4.66 ERA their starters posted last season. It would be highly unlikely for those five to make all 162 starts, but the Jays do have a number of backup plans, including Dustin McGowan, who finally appears healthy after a rotator cuff injury sidelined him in 2009, and Jesse Litsch, who should return mid-season following his own elbow surgery.

None of these guys will be as good as Halladay, at least not this season, but with three recent first-round picks in the fold, there’s reason to believe Toronto’s rotation will be better in 2010, even with Halladay in Philly.

Prince Fielder is a big dude. In fact, according to Baseball Reference.com, he is the only position player in baseball history to weigh over 250 pounds while measuring under six feet tall (he’s listed at 5-foot-11, 270). Fielder puts his size to good use, though; Over the past three seasons he has hit 130 home runs, which place him second among all major leaguers. It’s no surprise that many Milwaukee Brewers fans dread the 2011-2012 offseason, when Fielder will reach the six years of service time required to hit free agency.

Last winter, Mark Teixeira signed an eight-year, $180 million contract, and he’s not a significantly better hitter than Fielder. But, considering the risks a multi-year deal poses, teams may consider Fielder’s weight a deterrent. Only 14 position players in baseball history have weighed more than 260 pounds, and all of them have at least a few inches on Fielder. This leaves us with few players for comparison in terms of body mass.

The two best comparables on the list are Carlos Lee and Dmitri Young. Lee hasn’t faced many weight-related issues, and in fact has remained healthy for most of his career. The only significant time he missed over the past seven years was the result of a Bronson Arroyo pitch that broke his pinky finger in 2008. Young provides a more cautionary tale. Baseball America’s No. 29 overall prospect in 1997, he started his career strong, hitting 72 home runs and 157 doubles in his first five MLB seasons. He posted inconsistent numbers over the next seven seasons and was out of baseball at 34.

Two other names stand out as comparables. Mo Vaughn struggled during his first two years in the league, but broke out at age 25 and became one of the league’s premier sluggers. By age 31 his performance was in decline, and he missed all of his age-33 season to injuries, before finding himself out of the game by 35. Prince’s father, Cecil Fielder, was also out of baseball by age 35.

Prince will be 27 in the first year of his new deal. Chances are, if he continues to produce, some team will take the risk that he can buck the odds and remain a marquee attraction deep into his 30s.