A tale of two halves for St. Louis Cardinals All-Star Michael Wacha

Last night, the St. Louis Cardinals clinched the National League Central Division title for the third consecutive season with an 11-1 victory in the nightcap of yesterday's day-night doubleheader against the Pittsburgh Pirates. Excitement ensued on the field at PNC Park, in the visitor's clubhouse, and especially all over social media, and quite honestly, you need to look no further than Carlos Martinez's Instagram account for the details. Speaking of Carlos Martinez, he is unfortunately unavailable for the playoffs as he was shut down for the rest of 2015 after an MRI revealed a shoulder strain.

Thus, unless manager Mike Matheny shocks us all by implanting Tyler Lyons into the back-end of the playoff starting rotation, the four are pretty much set: John Lackey, Lance Lynn, Jaime Garcia, and Michael Wacha (this is my current order, but it is definitely a fluid situation). Lackey and Garcia have been fantastic all season, and I don't find myself worrying about their respective roles in the playoffs. Lynn, like Wacha, had a terrific first half, stumbled considerably in the second half, but his last few starts have shown small, but positive samples. On the other hand, Wacha has struggled for basically the entire second half, with very little sign of improvement or "turning a corner."

2015 Statistics by Half

The top of the table is pretty telling as it is (low fWAR, high FIP), but there are two statistics in the bottom half that are particularly worrisome going forward. Let's start with BB%, as Wacha has experienced a 93% increase from where he was in the first half. While he found himself in the top-15 of the National League before the break at 5.5%, his 10.6% is at the opposite end of the spectrum in the second half (though still lower than Lynn's 11.1%). There really is no way to sugarcoat this sour fact.

A contributing component to Wacha's walk rate is the decrease in percentage of swings by batters on pitches out of the zone. Wacha went from inducing a healthy amount (4th in NL) of swings on these pitches to finding himself near the very bottom of the league. To me, beyond the notion that hitters are adjusting and prior to getting into any PitchF/x data, this audibly screams the possibility of a given pitcher becoming more predictable, meaning that hitters are picking up on pitches much better and in turn are chasing fewer balls. By chasing fewer balls, especially when your first-half and second-half in-zone/out-of-zone percentages are nearly identical, hitters will walk more. This is inevitable.

Pitch Usage

As suggested above, Wacha seemingly has become more predictable in the second half as he has deployed a 10% increase in fourseamer use, coupled with a 22% increase in changeup use. While I will always promote more changeups, especially with a changeup as good as Wacha's, it's hard to be comfortable with seeing such a significant increase in fourseamer use. As written by Alex Chamberlain on FanGraphs back in early August, "Michael Wacha Has Four Above-Average Pitches," so a shift to becoming more predictable as a pitcher does not make much sense at all.

There is a ton of information I could talk about from this table, but for your time (and mine), I will focus on only two more: 1) Fourseam velocity and 2) Cutter movement. To this day, people continue to rave about Wacha's sustained (actually, increased) velocity. It is used as a crutch to hypothesize that nothing is actually wrong, but rather he is just dealing with some bad luck. Unfortunately, fastball command has been an issue all season (from April), and nothing suggests that it has improved or will improve with increased velocity. Regarding cutter movement, at 1.83 inches of average dragless horizontal movement in the second half, hitters perceive very little right-to-left movement on this pitch, from hand all the way to the mitt, which, frankly, is not the recipe for cutter success.

Pitch Results

While Wacha has enjoyed second-half success with his changeup, each of his other pitches has faltered when you look at pitch-by-pitch results, with his cutter being hit the hardest. It's tough to evaluate pitches in this manner, but seeing a considerable jump in batting average and slugging percentage between the two halves is not ideal.

Bottom Line

No, all is not lost for Michael Wacha, but adjustments are necessary as the Cardinals gear up for the postseason. Two relatively easy adjustments I would suggest are going back to his first-half pitch mix (but still keeping his changeup usage in the 15-18% range) and dialing back on his fourseamer and cutter velocity. While I don't expect this to magically lead to increase command (or control, for that matter), it should, at the very least, lead to more horizontal movement on his cutter and subsequently become a more effective pitch for him.

Credit to BrooksBaseball for data used in this post (note: data was gathered prior to yesterday's start).