For Brandon McCarthy, it's a tale of two seasons

It's no surprise that I'm writing about Brandon McCarthy. After coming over from the Arizona Diamondbacks in exchange for Vidal Nuno, he's pitched to a 1.90 ERA and 2.33 FIP in eight starts; that's in stark contrast to his first 18 starts where he had a 5.01 ERA and 3.82 FIP. The latter number is exactly why the Yankees made the trade, and it has certainly worked out. And while the organization was certainly hoping he'd pitch to the FIP he had already recorded, it has in fact been over a full point lower. This could be because of adjustments he has made with his new team--there was the Great Cutter Controversy in which the Arizona Diamondbacks discouraged him from using his cutter, a pitch the Yankees reasonably thought would help him improve. The Brooks Baseball data backs up this change:

While the cutter was a mere 4.81% of his repertoire in June, that bumped up to nearly 25% in August. He's strayed away from his sinker as well, and has relied on an equal mix of all four of his main pitches to keep batters honest. But to look at the actual change, let's take a look at a start McCarthy had with the Diamondbacks on June 11th against the Houston Astros.

McCarthy's start against the Astros in June was an ugly one, by both traditional statistics and through his peripherals. He allowed five runs on eight hits, two solo home runs, two walks, and four strikeouts over six innings. In particular, I'm going to look at the two solo home runs allowed, both off the bat of Chris Carter.

On the first pitch of the fourth inning, McCarthy allowed the first home run to Carter off of a hanging curveball. And then in the seventh inning, Carter did it once again, this time against a cutter that was hit right over the wall in right field. Here's a peek at both homers:

The cutter was elevated on the second home run--merely an error of location--and the curveball was a meatball of a pitch, a pitch that was pretty much dead-red. While there's been plenty of focus on the fastball, sinker, and cutter, the curveball is still an integral part of his repertoire (~20-25%). And one of the big improvements McCarthy has made, especially when playing in the bandbox that Yankee Stadium is for right-handed pitchers, he's made sure he's addressed his Isolated Power Against. Here, via Brooks Baseball, is his Isolated Power Against by pitch across the season:

As it's plain to see, the power numbers against McCarthy have been down immensely, and that could be for a number of reasons. The first reason is certainly because his repertoire is more varied, and the second could be because of location. I doubt that he merely added in one pitch and it suddenly made him better. He had to make sure the location was down, because the previous two pitches featured were right in Carter's wheelhouse. It's obvious that he's keeping the ball down because the amount of ground balls per balls in play has increased dramatically:

So not only is McCarthy varying his pitch selection, but he's making sure that this selection induces a greater number of ground balls. That has had the adverse effect of increasing opposing batting average, but he's traded that (gladly) for a decrease in opposing power and has struck out quite a few more hitters in his most recent starts.

Like all players, Brandon McCarthy has made plenty of adjustments. There have been adjustments of pitch selection and location, and probably of mechanics, but the talent level never changed. He was the exact same pitcher for the Diamondbacks, it's just that he was performing well below what he should have been. Luckily the analytics department was able to find this inefficiency and capitalize on it, because McCarthy is suddenly the ace of a starved rotation. Oh, and thank you again to Vidal Nuno.