Did Koji Uehara’s May Raise Any Alarms?

The Boston Red Sox spent the past offseason strengthening the bullpen with the acquisitions of Craig Kimbrel and Carson Smith. While Kimbrel has proven a solid anchor in the closer role, Smith’s injury and subsequent surgery has placed more pressure on Boston’s oldest player. Ian York looks at Koji Uehara’s May to see if there are any signs that the aging reliever is slowing down.

Koji Uehara has had a long and extraordinary career, spending ten years mainly as a starting pitcher in Japan and then moving to MLB as a reliever for another eight years and counting. Out of the bullpen, he has ranged from very good to transcendent; his 2013 season with the Red Sox ranks among the greatest pitching performances ever.

But in 2016, at 41 years of age, Uehara is the third-oldest player in MLB – behind only Bartolo Colon and Ichiro Suzuki – and by several measures he is having his worst year in the US.

A poor year for Uehara is still a fairly good year by most standards; with an ERA+ of 110, he is still a better-than-average pitcher. Moreover, his FIP is roughly at the same level as most of his previous seasons, offering some reason for optimism for even better results in the rest of the year. On the other hand, his velocity – never very impressive – was significantly down to begin the season. With 21 appearances in the books, I looked again at Uehara’s numbers to see if there was any more cause for concern.

Although Uehara’s fastball averaged 89.8 mph in 2013, throughout his MLB career he has more typically thrown his fastball in the 88-89 mph range (annual velocity in the chart below is taken from Brooks Baseball). Seven games into this season, Uehara’s velocity (just 87 mph on average, and barely topping 86 mph in several games) was looking like a red flag. However, since then his speed has improved somewhat, with a run of games in which he got his fastball back up into the 87.5-88 mph range that he has shown in the past few years. A set of three games (May 22-27) during which his velocity dropped incrementally was stopped by his most recent game, when he averaged 88 mph again. That is still slow, even by his standards, but it is much less worrying than the 86-87 mph early in the season.

As well as his fastball (called “FF”, for four-seam fastball, by PITCHf/x), Uehara’s signature pitch is his split-fingered fastball (“FS”), which he has typically thrown about 50% of the time. His mix this year (based on PITCHf/x, but manually recategorized to correct for PITCHf/x algorithm errors) is typical of his MLB career. Although he is throwing more sliders (“SL”) than usual, they are still a minority (6.75%), and are actually a throwback to 2013, when he threw about 5.3% sliders.

(There is also a category for “curve” (“CU”) because he threw three of them in 2013, and one in 2014.)

If velocity and pitch-mix are not red flags, how about the effectiveness of his pitches? I calculated the total bases per 100 pitches (TB/100) for each of his pitch types since 2013:

While the 2016 numbers are unsurprisingly worse than his 2013 season, they are still quite a bit better than average (which is about 9.3 and 8.7 for fastballs and splitters, respectively), and easily comparable to his last couple of years. (The number for sliders in 2015 is off the chart, at a horrifying 40. But that’s only because in that season, cut short by a broken wrist, he only threw five sliders, of which two were hit.)

Total bases per pitch might be irrelevant if he was also throwing more pitches per batter, but that number is virtually unchanged since 2013 (3.93 pitches per batter in 2013; 3.94 this year). He is getting slightly fewer strikes per pitch, but again, the difference is small, and he has been quite consistent following 2013:

(“Swinging” strikes here include fouls.)

No one expects Uehara to repeat his 2013 season, but so far this year there is no evidence that he has fallen off a cliff; most of his numbers are in line with his very good last few years, suggesting that his increase in ERA may be bad luck and temporary. He may no longer be able to sustain the stress and workload of a full-time closer, but as an 8th-inning specialist he should continue to be an extremely important part of the Red Sox bullpen.


Ian York uses the PITCHf/x to monitor the strike zone, highlights great performances, monitors league-wide trends and tracks the performances of some interesting young hitters.

Follow Ian on Twitter @iayork.

About Ian York 208 Articles
Ian is an immunologist and virologist who lives in Atlanta with his wife and two sons. Most of his time is spent driving his kids to baseball and soccer games, during which he indoctrinates his children on the glories of Pedro Martinez, the many virtues of the Montreal Expos, and other important information.

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