Hisashi Iwakuma’s Arm Strength
Hisashi Iwakuma makes his first start of the season tonight, filling in for the once-again-hurting Kevin Millwood. When Iwakuma pitches well (and that’s more likely than not, given that the game is taking place in Safeco and the Orioles aren’t very good at hitting right-handers), you’re going to hear people talk about how Iwakuma has “built up arm strength” and vastly improved over what he was earlier in the season. You’re going to be fed lines about how Eric Wedge’s usage pattern with Iwakuma has finally helped create a guy who is ready to pitch in the big leagues. You’re going to be told that Iwakuma needed three months of rest to get ready to get big league hitters out.
Don’t buy into any of it. It’s all BS. Here’s Hisashi Iwakuma’s velocity chart, tracking his average fastball speed over the course of the season.
Or, if you prefer numbers, here’s Iwakuma’s average fastball velocity by month:
April: 90.5 MPH
May: 90.8 MPH
June: 90.1 MPH
That’s right, the guy who has been building up his arm strength is actually throwing slightly less hard in June than he did in April. Of course, that’s essentially a function of the fact that he was asked to pitch back-to-back a few times in June, when he had longer layovers between outings in April, but the reality remains is that even well rested Iwakuma isn’t throwing any harder in June than he was in the first month of the season.
As for performance, that’s fairly consistent too.
April: 10% BB%, 20% K%, 50% GB%, 4.11 xFIP
May: 9% BB%, 20% K%, 45% GB%, 3.92 xFIP
June: 14.5% BB%, 16.5% K%, 67% GB%, 4.30 xFIP
Iwakuma has been basically the same pitcher all year long, getting a good amount of groundballs and an acceptable amount of strikeouts while issuing too many walks and giving up too many home runs. Whether the command problems (which were never a problem in Japan) are a result of his marginal stuff not playing that well in the US or inconsistent usage is impossible to know, but the fact is that he’s shown enough movement and velocity to get Major League hitters out when he’s throwing strikes with consistency.
Iwakuma’s probably not a great MLB pitcher. He doesn’t have a devastating out pitch, and his skillset works best when he can pound the zone, which he hasn’t done regularly enough. But he’s probably a decent Major League pitcher, a guy who can get a bunch of grounders and mix his pitches well enough to get strikeouts when needed. And the truth is that Iwakuma’s been that guy from day one.
His results were bad in spring training because of an inflated BABIP, but there was never any reason to relegate him to the mop-up role that he ended up stuck with. Wedge’s refusal to use him was always foolish and a waste of a decent pitcher. That Iwakuma is only now getting a shot at the rotation is the result of poor decision making by the organization, and at this point, the best the team can hope for is that Iwakuma proves that they’ve had a viable #4 or #5 starter hanging out in the bullpen all along. Given the team’s struggles to find quality back-end starters this year, having Iwakuma step forward and grab one of those spots would be a nice boost for the club, and give them another potentially interesting piece to evaluate in the second half.
It’s just too bad that it took until July for it to happen. Don’t let the revisionists try to sell you a load of crap about Iwakuma not being ready for this job in April. The reality is that he’s the same guy now he was then, and his future success is simply going to be more evidence that the Mariners got it wrong coming out of spring training.