We'll Miss Hiroki, But Let's Be Glad We Won't Suffer His Imminent Decline

Kuroda vs BAL II I'll definitely miss Hiroki Kuroda. Pitchers are notoriously inconsistent, but not Kuroda: in seven MLB years, all his annual ERAs were 3.3-3.7ish, except one 3.07 that seemed lucky (his FIP was a more Kurodalike 3.78). He rang up 12 WAR over his three Yankee years, so his $41m was a real bargain, about half the $6-7m/WAR free agent going rate. And he was fun to watch; I'm a sucker for graceful mechanics like Kuroda's, and also for the badassness of swings and misses at sinkers barely above the dirt.

But I'm only a little, not a lot, sad he's leaving. He turns 40 in February; almost no non-juicing/non-superstar pitcher remains any good at 40-41; and Kuroda has already started suffering decline.

Kuroda impressively defied the odds by throwing in the 90s while pushing 40, but his hard sinker has definitely slowed, modestly but steadily: from 92.3-92.4 at ages 33-34, to 91.7-92.0 at 35-37, then to 91.5 at 38, and then, last year, to 91.0 at 39. Unsurprisingly, his K rate had a parallel downward path since 2010: 7.3; 7.2; 6.8; 6.7; 6.6. He avoided dramatic impact from his slowing sinker and declining Ks only by enjoying a simultaneous drop in walk rate since 2010: 2.2; 2.2; 2.1; 1.9; 1.6. But 1.6 BB/9 is about the limit of how much you can improve control to offset declining stuff, so unless he becomes the first non-juicer to find a way to increase velocity and Ks in his 40s, he's due for an ERA rise.

As his velocity and Ks declined, so did his performance, at least in 2014. Here are his Yankee WARs: 5.5 in 2012; 4.1 in 2013; 2.4 in 2014. His consistent ERAs actually reflect modestly worse performance through 2014: leaguewide run-scoring is down; but Kuroda keeps giving up runs at similar rates.

Given the modest yet clear ability decline, the realistic best-case 2015 scenario would have been a little worse than 2014's 3.71 ERA / 3.60 FIP. So a high-3s to 4ish ERA is plausibly optimistic, but given how rare it is to remain even league-average at 40-41, there's a high chance his performance would fall off the cliff – just because that happens to everyone, typically by the mid-late 30s, but almost always by 40-41.

I ran a Play Index search on Baseball Reference to see, in the past 25 years, how many pitchers kept performing at about league-average level (2.0 WAR) at each age from 30 to 41.

Age Starters with 2.0+ WAR
30 107
31 91
32 66
33 74
34 50
35 39
36 32
37 19
38 16
39 14
40 14
41 9

The cliff pitchers fall off by about 40 is dramatic – across MLB, there's typically less than one 40something starter a year who can perform league-average or better – and it's even worse than it looks for folks in their 40s. Of the 15 with 2.0 WAR at 40 or 41 (it was 14 at 40, plus 9 at 41, but it was a lot of the same guys), few were like Kuroda: more than half were either (a) Hall-of-Fame talents whose youthful peaks were so high that their declines were delayed or at least left them still average (Maddux, Johnson, Glavine, Clemens, Schilling, Smoltz) or (b) soft-tossers who always somehow succeeded with no real velocity (Wakefield, Moyer). There just are very, very few guys who spent their 30s as good-not-great starters relying on above-average stuff, yet in their 40s remained average or better.

So I'll miss the guy, but in a way, he did the Yankees a favor. If he kept coming back on one-year contracts, then either this year or next, he would've really hurt the team with that last awful year you get when you hold onto anyone too long. I know this may read like I'm the guy at the funeral who drank too much, then stumbled up to mumble that the guy wasn't as great as everyone else is saying, but that's not how I mean it. The proper eulogy is that Kuroda gave the Yankees an awful lot, and like Mussina, he went out on top, without subjecting us to the fading presence all ballplayers become when they insist on hanging on one year too many. We're lucky we squeezed three strong years out of him as he pushed 40, without suffering the awful last year you always get when a seemingly ageless wonder keeps going just long enough to prove nobody is really ageless.