With expanded repertoire, Michael Wacha continues to evolve as a pitcher

In 2013, St. Louis Cardinals righthander Michael Wacha turned heads with a terrific spring training. He started the season off in the minors but was soon making important starts for the Redbirds down the home stretch of the regular season. His bread and butter were his fourseam fastball and changeup. Wacha sprinkled in some curveballs, to be sure, but he predominantly relied on his nasty fastball-change combination.

How pitchers evolve as players has long interested me, especially when they decide to implement a new pitch. So my interest was piqued this spring when Jenifer Langosch of MLB.com reported that Wacha was working on a cut fastball to complement his fourseamer and changeup. During his rookie campaign a year ago Wacha threw a cutter, but only 1.8% of the time. Wacha indicated that he was comfortable with the pitch during spring camp and planned on using it when games counted.

Wacha has made 13 starts so far this 2014 season, which is a bit more than one-third of the total we hope to see him notch over the entire season. So let's check in with Wacha's pitch selection and see whether it has changed as compared to his debut season (and postseason) in the majors. The following chart shows Wacha's percentage share usage of pitches during 2013 in yellow and for 2014 in red. As usual, all data is from the indispensable Brooks Baseball.

WACHA PITCH USAGE: 2013 vs. 2014

As you can see, Wacha is still relying on his fastball the majority of the time. But his reliance has fallen off a fair amount. As has his dependence on his nasty changeup. Wacha is deploying both his curveball and cutter more often this year. In Langosch's spring-training article on Wacha's embrace of the cutter, she explained his goal in deploying the pitch more often:

Wacha isn't necessarily looking for the pitch to induce swings-and-misses. But it has produced weak contact and has given batters an extra pitch to consider when they step in against him.

The following chart is a screen grab from Brooks Baseball of the sabermetric outcomes— Wacha has experienced when throwing each of his pitches.

*Brooks Baseball shows that Wacha has thrown two sliders this season. I suspect they might be misclassified cutters. Off the top of my head, I can't recall seeing a Wacha pitch and thinking to myself, "Did Wacha just throw a slider?" If you've had this reaction, please share in the comments.

Wacha is not getting all that many whiffs with either his curve or cutter relative to his fourseamer or change. But it appears that he is inducing weaker contact with his curve than with his cutter—at least going by line drive rate (LD/BIP).

Looking at this through the prism of batted-ball results, however, paints a different picture. The following is another screenshot from Brooks Baseball. This one shows the results batters have experienced against each of Wacha's pitches so far this season.

By results, opposing hitters are hitting for a higher average and more power against Wacha's fourseamer and cutter than his change or curve.

Wacha has evolved as a pitcher through the first part of his sophomore MLB campaign. He is deploying four pitches instead of relying predominantly on just two. And it's hard to argue with the results. As Wacha prepares to toe the rubber tonight at the Trop, his 2.61 ERA ranks 16th in MLB and is right in line with his 2.76 FIP, which places him 12th in the big leagues. Wacha is emerging as Ace No. 2 of the Cardinals rotation.