Over the past three years the Yankees have employed Joba Rules to one degree or another. In 2007 it prevented him from pitching on back-to-back days. In 2008 it meant him starting the season in the bullpen. In 2009, most frustratingly, it led to three-inning starts in August. The Yankees had the best of intentions in mind, of course. Joba had just 15 minor league starts, about 88 total innings, before making his Major League debut, and the team wanted to make sure they weren’t increasing his workload too quickly. There’s nothing wrong with trying to keep your pitchers healthy.

The recent obsession with innings limits originated with research conducted by Sport Illustrated’s Tom Verducci and then-Athletics pitching coach Rick Peterson. They found that pitchers aged 25 and younger who pitched more than 30 innings over their previous career high were at risk of performance drop-off or injury in the next year. Intuitively, the theory makes sense. Going from the couch to running five miles is a terrible idea. Runners will succeed more often if they start small and build up to those five miles. With data to back up the idea, teams could act by limiting their young starters’ innings.

Many fans might be frustrated, then, to see Joba Chamberlain appear on the 2010 Verducci list. Between the regular season and the playoffs Joba threw 163.2 innings. Verducci identifies that as an increase of 47.2 innings over his previous career high. So what gives? The Yankees went through so much trouble to keep Joba’s innings at a reasonable level. How can Joba still be listed as an at-risk pitcher?

An increase of 47.2 innings means that Verducci identified Joba’s career high as 116 innings. That comes from 2007, Joba’s first professional season, when he threw 88.1 minor league innings. 24 regular season ML innings, and 3.2 postseason innings. Looking at his Baseball Cube page, we can see that Joba threw 118.2 innings at Nebraska in 2005, followed by 89.1 innings in 2006. We can tack on 37.2 innings to his 2006 total, since he pitched in the Hawaiian league, bringing his total to 127. This morning, Mike mentioned that he threw another 45.1 innings in summer ball, the M.I.N.K. League (Missouri, Iowa, Nebraska, Kansas) in 2005, bringing his total that year to 164 innings.

The progression moves oddly for Joba. How do the Yankees determine his previous career high? Is it his absolute high, which occurred four years prior? Was it his first professional season, most of which he spent in the minors? What about the gap between his innings in 2006? The difference between his bullpen and his rotation innings in 2007 and 2008? The most important question, to me at least, is of the difference between college, minor league, fall league, summer league, and major league innings. The competition is different, but does that change how the pitcher works?

Not even Verducci himself can answer those questions. He admits that the Year After Effect is more a rule of thumb, a general guideline. Each pitcher has throws different pitches with varying amounts of force. Furthermore, each pitcher’s body reacts differently to the stress of pitching. Every year Verducci identifies at-risk pitchers who cruise through the season. Among that group from the 2009 list: Tim Lincecum, Clayton Kershaw, Jair Jurrjens, and Jon Lester. He also identifies five pitchers as confirming his rule, but Mike Pelfrey, Cole Hamels, Chad Billingsley, John Danks, and Dana Eveland spent a combined zero days on the disabled list in 2009. They didn’t perform to their 2008 levels, but that can also be attributed to them being young, relatively inexperienced pitchers.

None of us has any idea what’s in store for Joba health-wise in 2010. From what I can tell he’s missed time only twice in his career with injuries. First came at Nebraska in 2006, when his draft stock dropped because of triceps tendinitis. He again suffered from tendinitis in 2008, this time in his shoulder. Yes, he saw a sharp increase in his 2009 totals over his previous professional highs, but he has thrown that many innings before, and at a relatively high level. How will that play into his 2010 season? I’m comfortable saying that I don’t know.

Credit: AP Photo/Charles Krupa

For about eight weeks during the 2008 season, Joba Chamberlain displayed dominance as a starter. After spending the first 60 some-odd innings of his big league career in the bullpen, the Yankees transitioned him to the rotation in June and there seemed to be only a routine drop-off in performance. His fastball still blew away hitters, and his slider still dropped off the table. It appeared the Yankees might see another homegrown star. Unfortunately, after 65.1 innings in the rotation Joba’s shoulder gave a bit, ending his 2008 stint in the rotation. After the season, however, Brian Cashman showed unquestioned faith in his 2006 draft pick, saying that only he and Chien-Ming Wang were guaranteed rotation spots in 2009.

As we remember all too well, Joba’s second season in the rotation didn’t go quite as well as the first. For starters, his fastball lost 2.5 miles per hour, the biggest loss in the majors among pitchers with 50 innings in 2008 and 2009. He seemed tentative on the mound, constantly shaking off Jorge Posada. In many instances he shook his head until Posada signaled for slider, especially in 3-2 counts. But the slider didn’t appear to have the bite we saw over the past two years.

Even still, he managed to pitch decently through July. At that point the Yankees tried two techniques in order to limit Joba’s workload, though neither seemed to take. That might have been a result of the uncertainty he faced, but it also might have been because he’d never pitched so many innings in a regular season. In any case, his performance did decline in the season’s final two months, his ERA inflating by more than a full run over that period. Clearly, something had changed.

Last week we looked at how Phil Hughes changed over the years. Now it’s Joba’s turn. What changes, other than fastball velocity, did he realize in 2009?

As regards his fastball, it appears that velocity is all he lost. In terms of movement he remained the same. In 2008 his fastball broke 4.4 inches towards right-handed batters (compared to a pitch with no spin), compared to 4.2 inches in 2009. His vertical movement was almost exactly the same as well, 10.0 inches in 2008 and 9.9 inches in 2009. He might not have been throwing it as hard, but velocity isn’t everything. His vertical movement remains comfortably above league average, though his horizontal movement remains below.

His bread and butter, the slider, did appear to have changed from 2008 to 2009. It did lose some velocity, about .08 mph, or about one percent. By comparison, his fastball velocity decreased by about three percent. In 2007 and 2008 Joba’s slider seemed to travel about 5/6 of the way to the plate and then drop at the last second. The 2007 PitchFx data is rough, but we can see the effect in 2008. Joba’s slider dropped 0.9 inches, while a league average slider “rose” 2.8 inches. In 2009 his slider had an inch less drop, at 0.1 “rise” compared to a league average of 2.3. So not only did Joba’s vertical movement rise, but the league average dropped.

As we know, pitchers employ different kinds of sliders. While some break primarily on the vertical plane, like Joba’s in 2008, others move side to side. In 2008 Joba didn’t generate much side to side movement, just 0.8 inches against a league average of 2.1 inches. In 2009 it appears Joba changed styles, as his slider broke 2.1 inches horizontally, against a league average of 2.4. The Texas Leaguers Pitch f/x tool says Joba got 18.3 percent swings and misses on his slider in 2009, compared to 26.2 percent as a starter in 2008.

Joba’s other secondary pitch, his curveball, also saw diminished movement in 2009. The horizontal break remained consistent, 4.1 against a league average of 5.1 in 2009 and 4.2 against a 5.3 league average in 2009. In terms of vertical break, however, it wasn’t nearly the same. In 2008, when he started working it into his arsenal as a starter, the pitch dropped 6.7 inches, a full two inches better than the league average.

My question is how to evaluate the pitch’s effectiveness. It’s not necessarily a swing and miss pitch like the slider, so whiff rate isn’t the only factor. In that regard, however, he did a bit better in 2009, inducing a swing and miss 14.9 percent of the time, compared to 5.6 percent as a starter in 08. He didn’t throw it as often for a strike, though, 55.9 percent in 2009 against 58.7 percent in 2008. Hitters swung at it more often in 2009, however, 34.3 percent against 23.8 percent in 2008. Might the greater vertical break in 2008 have fooled more hitters, causing them to look at more strikes?

(I was hoping that Joe Lefkowitz’s Pitch F/x Tool could tell us, but it appears to not be loading 2008 data. Drat.)

When we discuss Joba Chamberlain 2009 season, the topic often centers on his fastball. While his reduced velocity did cause concern, his pitches still broke in a similar manner. What might be more concerning is the change he saw in his secondary pitches. The breaks on his slider and curveball changed in 2009, and as we saw in the case of the slider, it led to fewer swings and misses. It appears Joba has a lot to work on for the 2010 season. Thankfully, he showed up early to get a head start.

Credit: AP Photo/Charles Krupa