The return of Michael Wacha's changeup bodes well for the rotation of the St. Louis Cardinals

Two days ago, St. Louis Cardinals right-hander Michael Wacha breezed through his 2015 spring training debut—retiring all six Red Sox hitters he faced, with four of them coming via strikeout. Now, to be fair to Boston and realistic in our judgment, three of Wacha's four strikeouts came against essentially minor league players as they have had a grand total of 66 MLB plate appearances to date (Garin Cecchini, Travis Shaw, and Luke Montz). To be honest, I do not care much about Wacha's spring stat line. Instead, what I'm focused on and extremely excited about is the return of his changeup.

In September of last season, after Wacha returned from the disabled list, Craig wondered where the 23-year-old righty's changeup went. At the time of Craig's posting, Wacha was two starts back and had thrown his changeup only 6% of the time. Per BrooksBaseball, his changeup frequency increased to 14.61% the rest of the season, but this was still down from his career rate of 22.24%. Part of the reason may have been mechanical or even rustiness due to an extended stay on the disabled list, but another contributing factor could have been that it just was not nearly as effective as the pitch had been prior to getting injured:

A sample size of 45 changeups after returning from the disabled list is not ideal for comparative purposes, but the across-the-board differences are so noticeable that I think it is still important to discuss. The most significant dynamic between a fastball and a changeup is the difference in their respective velocities. As you can see, upon returning from the disabled list, Wacha lost nearly one MPH from the velocity difference between his fastball and changeup (-6.67 MPH from -7.49 MPH). While this may not seem significant, it is definitely a factor when considering a pitch that relies heavily on hitter deception.

As Goold noted yesterday, "Wacha has 'tilt' back in his pitches," and when comparing pre- (6.85 feet) and post-DL (6.67 feet) vertical release points, you can see that this was indeed an issue for Wacha last September and October. Moving across the table, PITCHf/x shows that Wacha experienced less horizontal and vertical movement with his post-DL changeup as well. Putting all these aspects together, Wacha was not getting hitters to swing and miss like he had grown accustomed to, as his whiffs/swing percentage was cut nearly in half (down to 19.05% from 34.46%).

In Goold's article, it was specifically noted that Wacha had a ~9 MPH difference between his changeup and his fastball and that three of his four strikeouts came via changeup. Thus, early reports, though limited to two spring training innings, are favorable. Now, will Wacha's changeup return to how good it was in 2013 and pre-injury 2014? This is a tricky question because even prior to his injury, the sample size (675 pitches) was still small enough to have the potential of inflating the actual effectiveness of the pitch.

Either way, he has significant room for improvement from last September and October, and it is comforting to see that the shoulder injury has not kept him from being physically able to throw the best pitch in his repertoire. The effectiveness of his changeup will go a long way in determining the success of Michael Wacha as a starting pitcher.

Credit to BrooksBaseball for PITCHf/x data and @mstreeter06 for the GIF.