Does Red Sox Reliever Koji Uehara Have Anything Left?

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The Boston Red Sox entered the 2016 season with high hopes for their bullpen, but injuries and ineffectiveness have dashed those hopes. A couple trades and the return of a playoff hero have some fans hoping again though. Ian York uses PITCHf/x and his unique charts to determine if that hope is misplaced when it comes to Koji Uehara, or if the veteran has one more run left.

Koji Uehara in 2016 is just a shadow of the pitcher he was in 2013. Fortunately, in 2013 he was so transcendent that he can be much worse and still be very effective. Overall, his numbers in 2016 are fairly good — ERA of 4.15 (ERA+ of 112), and 1.000 WHIP. The question is, however, whether he can continue to be effective after his seven-week stint on the disabled list for a pectoral muscle strain.

Earlier this year, I reviewed Uehara’s first 21 games of 2016 and compared them to his previous seasons, and concluded that “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.” Until his injury in mid-July, that seemed to be reasonably accurate. He has now appeared in 42 games; here are his game-by-game results. The vertical red line shows his DL period.

He has seemed to be effective in the three games after his return from the DL, allowing only two hits and no walks, while striking out five in three innings. However, there are some signs of real concern. For one, his velocity is dramatically lower than his normally-slow speeds. Again, the DL stint is marked with vertical red lines:

Compared to his pre-DL average fastball velocity of 87.5 mph, he has averaged just 85.8 mph on his fastball since his return; his splitter has followed suit, going from 79.2 to 78.1 mph.

Uehara has never depended on velocity to be effective, relying instead on deception, movement, and location for his results. There, too, in spite of his good results since his return, we see some troubling signs. Here are the locations of all the pitches he has thrown since his return:

Note how many of the splitters (to left-handed batters especially) ended up in or near the center of the strike zone. Classically, Uehara misses the middle of the zone altogether. His splitter in particular drops below the strike zone, drawing the swinging strikes that we see for four splitters in these three games.

This may be a continuation of a worrying trend for Uehara in 2016. Although after his first 21 games his splitter was still a positive pitch, at this point in the season it is significantly worse than the average splitter in terms of total bases per 100 pitches:

Uehara’s fastball has still been a very effective pitch throughout 2016, but with much lower velocity and a less-effective splitter for contrast, it is uncertain how long he can continue to be effective relying almost entirely on location. If he can bring his fastball velocity back up to his season average, there is more room for optimism, but it might still be premature to count on him in high-leverage situations.


Follow Ian on Twitter @iayork.

Featured image courtesy of Gregory Bull.

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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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