Will the Injury to Red Sox Closer Koji Uehara Mean the End of His Dominance?

With the injury to Red Sox closer Koji Uehara, the Boston Red Sox received another setback in a season chock full with setbacks. However, we would be remiss to forget the greatness that Uehara has shown us these past three seasons. Ian York takes a look at a key at-bat in the 2013 ALCS to show how good Koji is.

Koji Uehara has gone from being an otherworldly closer in 2013, to being merely a very, very good one in 2014 and 2015. The news that he has been placed on the disabled list with a broken wrist, after being hit by a line drive, is distressing. Not just because of his pain and suffering, and not because of the cost to this season (which is pretty much a lost cause by now anyway), but because of the concern that he may not come back well from the injury next year. After all, not many pitchers perform at Koji’s elite level at the age of 41 (as he will be next year), and recovering from a broken wrist makes it even less likely that he will return to excellence.

On a happier note, let’s look at Koji in the 2013 ALCS, when the Boston Red Sox beat the Detroit Tigers four games to two. That outcome didn’t seem very likely on October 15, 2013, Game 3 of the series. The series was tied, and while the Sox were leading 1-0 in the 8th inning, the lead felt very tenuous. Craig Breslow had walked Austin Jackson, Junichi Tazawa had given up a single to Miguel Cabrera, and Prince Fielder, with 25 home runs and an .819 OPS in the regular season, was at the plate with two out and runners on first and third.

Uehara replaced Tazawa, and with three pitches struck out Fielder, stopping the Tigers’ rally, and then completed the save with a single, double play and strikeout in the 9th.

Here is Fielder’s 8th-inning at-bat, animated from PITCHf/x data:

 Those three pitches encapsulate what has made Koji great: Precise location of his fastballs on the top and bottom corners, and a slow but absolutely baffling splitter that consistently draws swinging strikes, even when outside the strike zone (as this one was).

We can compare the last two pitches, fastball and splitter, in more detail. Here, the solid line shows the path that the ball would take if it was affected only by gravity; pitches invariably deviate from that line because of their interactions with the air, mainly through the spin that’s put on them:

Even though Uehara’s fastballs are not particularly fast, rarely breaking 90-mph, he throws them with extreme backspin. (In 2013, he averaged 2,437-rpm on his fastball, putting him 13th of the 186 pitchers who threw at least 500 fastballs.) Backspin pulls the ball upward from its default path, so that even though Uehara’s fastballs are relatively slow, they fail to drop nearly as much as the batter expects, leading to swings and misses, easy pop flies or fouls.

Uehara combines the fastball with his splitter to devastating effect. The pair of pitches here shows why. Although the splitter is slower (taking an extra .04 seconds to reach the plate), the pitches look essentially identical at first. It is not until the pitches are about 20 feet .15 seconds away from the plate that the pitches separate themselves, with the splitter continuing to drop while the fastball “rises”.

The limit of human reflexes, even for a major-league batter, is about .20 seconds.  

That means that Fielder had to decide whether or not to swing at the pitch when it was 25 to 30 feet in front of the plate, at a point where Koji’s splitter and fastball still follow the same trajectory, even though these pitches arrived at the plate nearly a foot apart (11 inches, to be precise). It is amazing that Fielder managed to adjust his swing enough to even foul tip the pitch.

Koji finished the ALCS (for which he was named MVP) with a microscopic 0.667 WHIP, which, incredibly, was higher than his regular season WHIP of 0.565. Even though he has not been as dominant since then, neither has anyone else before or since. If he can return in 2016 as the excellent pitcher he has been in 2014 and 2015, then fans should be more than happy.

Ian York has written about rookie struggles, an impressive start by Eduardo Rodriguez, Joe Kelly’s fastballs, the effect of better bullpens on offensive strategy and a look at how Blake Swihart has been doing this season.

Follow Ian on Twitter @iayork.

Check out our This Week in Baseball Writing as well as author Brandon Magee’s look at baseball player Brandon Magee’s road to professional baseball.

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