From 2012 to 2016, one could argue that only Zach Britton and Wade Davis were better relievers on a per-inning basis than Yankees closer Aroldis Chapman. At 15.67 K/9 and a 47 ERA-, there was almost no one you would prefer in the ninth inning of a tight game. I would say that perception changed a bit when he nearly cost the Cubs their World Series Game Seven, on the heels of manager Joe Maddon squeezing out every ounce of Chapman throughout the postseason.
That had a non-trivial effect on Chapman’s 2017, I believe, and it showed until well into the season. This year he found his results notably diminished, to the tune of a 73 ERA- over 50.1 innings, which, of course, isn’t disastrous. At times, however, it appeared to be when looking from narrative perspective. Here is his rolling ERA- over the season:
It then surfaced in August that Chapman was struggling with elbow discomfort, something that shouldn’t be altogether surprising given the previous developments. That’s also about the time we see the ERA- curve, as it was recovering back up to nearly 100, and then he rebounded suddenly in time for the postseason.
Chapman also lost his closer position as of August 19th when he allowed a run in four straight outings. He regained the job on September 6th after working his confidence back, and became the Chapman of old in time for the Yankees’ deep playoff run.
There were a few developments that were important for Chapman, both last year and moving forward. Firstly, he has notably been bumping up his percentage of sliders since 2014, as his fastball has become less effective:
Which means, at the same time, that his whiff rate on nearly all of his pitches have been sinking:
It’s really not a great sign for a very expensive closer, but here we are. It’s difficult to explain why his effectiveness slipped. A good theory is that Chapman’s fastball is no longer as “special” as every team has a flamethrower. With more batters adjusted, they have the timing for a straight 100 mph fastball.
This pretty much all points to a larger adjustment that needs to be made. As long as Chapman is healthy, I bet he could be at least one standard deviation better than the average closer. That’s fine, but not for the money he’s being paid. There’s also the fact that he has an opt-out I would prefer he exercises, and there’s no chance he opts out if he continues to decline. The key to success is in adding a cutter along with his four-seam fastball to make sure a hitter can’t just sit on the straight pitch.
The good news is that he was incredibly good in the postseason. He struck out 16 batters in just eight innings and was worth 0.48 WPA, so there’s a good argument to be made he helped them stay in the race as long as they did. That doesn’t erase his lackluster season, of course, and that is going to be what Yankees fans will be closely watching in 2018. If he can succeed, the relief equation gets much, much simpler.