Has Increased Slider Usage Caused Arm Trouble for Cubs’ Matt Garza?

In a couple of hours, Matt Garza will make his long-awaited return from the elbow and shoulder injuries that have sidelined him since last July 21st. After the long stint on the DL, the same question has to on the minds of baseball fans everywhere: how did this happen? Garza missed time in early 2008 with some elbow trouble, but from then until May of 2011, he didn’t have any injury problems whatsoever. But then he missed a couple starts with an elbow contusion in 2008 and that was only the start of his injury problems as a stress fracture in his right pitching elbow ended his 2012 season in July and a shoulder strain kept him sidelined up until now in 2013. Why has Garza suddenly become so injury-prone?

The last two years, Matt Garza looked as good as he we had ever seen him. He had been a solid pitcher for the Rays, managing a 3.86 ERA (109 ERA+), a 7.1 K/9, a 3.1 BB/9, and a 1.1 HR/9 (4.32 FIP) from 2008 to 2010, but in 2011 and 2012 he was significantly better. He put up a 3.52 ERA (113 ERA+), an 8.7 K/7, a 2.8 BB/9, and a 0.9 HR/9 (3.47 FIP) in 49 starts and 301.2 innings pitched. Why has Garza gotten so much better? A big reason has been that he has been willing to go to his slider more often. After throwing it just 13% of the time from 2008 to 2010 according to Brooks Baseball, he threw it 24% of the time the last two seasons with spectacular results. But has Garza throwing his slider more not just caused his improved performance but also his injury issues?

Why would Garza throwing his slider more cause him to get injured? He might put more stress on his arm by either throwing the ball at a sharper angle or an angle that he’s not used to. Could Garza’s release point being higher or lower be the reason that he has been injured? Calculating Garza’s release angles using the Brooks Baseball data, no pattern at all seems to emerge.

The correlation between the average angles and Garza getting injured doesn’t seem to be very high as Garza got injured in 2008 when his release angle was the lowest in the data set and then in 2011 and 2012 when his angle was right around the middle. Looking at the slider, there is even less of a pattern as Garza got injured in 2008 when his release point was lower but then in 2011 and 2012 when it was around the middle again. Are we saying that Matt Garza gets injured when his release point is around his career average? That’s pretty ridiculous so we will have to delve deeper than this.

The 2008 injury seems to be the easiest to explain by far. His release point was the lowest of his career and his slider played a major role in that. The difference between his slider angle and his average release point was significantly more than any other year, coming in at 1.18 degrees less than average compared to his career average of just .56 degrees. The difference becomes even more pronounced when you compare it to his fastball as it was 2.96 degrees less, almost triple the 1.01 degrees lower than his fastball that it has averaged for his career. In 2011 and 2012, though, Garza is basically throwing all of his pitches right around his career average release points. He may be throwing his slider more, but it’s not getting his overall release point out of whack and it has in fact gotten closer and closer to his fastball. It has been .33 degrees and .32 degrees less than his fastball the past two seasons, the second- and third-best marks of his career, and that also helps explain why it has been so effective even as Garza has ratcheted up its use so significantly. So why is he getting injured? Maybe there’s something about the way he throws his slider that isn’t quantified simply by his release point, but if nothing else, it’s clear that his slider is not solely to blame for his injury concerns.

Why has Matt Garza dealt with so many injury problems the last couple of seasons? The fact that he’s throwing his slider more and then got injured has to be noted, but there’s no evidence that throwing his slider more has left him susceptible to injury. Throwing a baseball is an unnatural motion, and pitchers get injured all the time. Garza just got unlucky that he got injured several times in a row, and Cubs have to hope that his injury problems are behind him now. If Garza’s arm hurts when he throws his slider, they should limit the amount of times he throws it, but unless that’s the case, there’s no reason to stop him from throwing his slider as often as he has. By telling Garza to throw his slider more, the Cubs have turned Garza from a good pitcher into a potentially great one, and if they tell him to start throwing it less like he did during his time with the Rays, they’re doing nothing but being overzealous protecting their pitcher and limiting his effectiveness in the process.