Let’s All Aroldis Chapman

It can be difficult to write up some moves. For example, when one great reliever takes over a high-leverage role from another great reliever in the midst of having some bad luck, it seems there’s little to say. Sean Marshall is good, but Aroldis Chapman is better. Done?

Sean Marshall has a 1.42 xFIP based on a double-digit strikeout rate, a minuscule walk rate, and a great ground-ball rate that should lead to a better home run rate than he’s showing now. Aroldis Chapman has a 1.53 xFIP based on a double-digit strikeout rate, and above-average walk rate (right now), and an average-ish ground-ball rate that has been better over his career. What he does have, that Marshall doesn’t, is the velocity of a closer. Still humping it over the plate above 97 MPH, he has some of the best gas in the game.

But that doesn’t mean there aren’t some hurdles for him to overcome on his way to being a lights-out closer.

The biggest is that the Reds haven’t liked using him in back-to-back days, reportedly at his request. This year he’s only managed the feat once. Last year, it was only ten times. In comparison, Sean Marshall pitched back-to-back games 19 times last year. You might want to keep Marshall around — at the very least he’ll be useful if Chapman has pitched two games in a row already.

One of the stated reasons for the lack of back-to-backs is that Chapman loses his control on those days. His walk rate in the second game of a back-to-back is 5.82 per nine (11 in 17 innings), but his career walk rate is 5.57 per nine, and that’s a tiny sample. Still, coupled with a subjective preference not to pitch on back-to-back days, there’s a little something there.

That control itself could be a problem. Back when Carlos Marmol had elite strikeout rates, he taught us that a closer can make bad control work. The average walk rate for the top 600 relievers by saves since 1992 was 3.3 BB/9, so his career walk rate is over two men per nine worse. Even on a strikeout-to-walk level, Chapman’s career 2.43 strikeouts per walk comes in behind that group’s average 3.02 strikeouts per walk. Even with his plus-plus gas and plus-plus slider, his minus-minus control does put him at risk for losing the role.

On the other hand, there have been 52 closer-seasons with a walk rate over five since 1992, which is more than two per year. There have been 165 with a walk rate over four. There have been 259 closer-seasons with a strikeout-to-walk ratio under 2.5 over that same time frame. Players like Mitch Williams, Jason Isringhausen, Carlos Marmol, Jose Mesa and Todd Jones have made bad walk rates work for them. Williams made a career of it.

None of this is to say that Aroldis Chapman is a bad reliever and in danger of losing his job. He’ll probably be fine. But Sean Marshall owners should also probably hold on to their reliever, if just for a little bit. Chapman’s control, and reluctance to pitch in back-to-back days, keeps the door cracked open just a bit.