Koji Uehara's Unhittable Splitter

Koji Uehara is 38 years old, needs a strong gust of wind at his back to crack 90 MPH on the radar gun and is the third-highest -paid reliever on the Boston Red Sox. He's also eviscerating hitters. Uehara boasts the sixth-best strikeout-to-walk ratio (9.67) ever among relievers tossing 60+ innings in a season, and his park-and-league adjusted ERA is 269 percent above average -- that's 12th best all-time among 'pen arms.

While he doesn't have Aroldis Chapman's gas or Craig Kimbrel's wipepout slider, Uehara might just possess the nastiest pitch in the game in his splitter. The right-hander throws his tumbling, low-80s split nearly half of the time (47 percent of his total pitches), transforming opposing lineups into a fleet of weak-hitting pitchers in the process. When Uehara unleashes a splitter, opponents are batting .101 and slugging .193. The last time a hitter managed an extra-base hit against the pitch was nearly three weeks ago, when Lyle Overbay laced a double in a loss to the Sox on August 17.

Here's more on Uehara's splitter, as the Sox stopper looks to vanquish the Yankees' slim playoff chances...

• Part of what makes Uehara's splitter so deadly is that the pitch tails in on righties (away from lefties) much like his fastball, but it then drops off the table. On average, Uehara's splitter and fastball both have about 5-6 inches of horizontal break compared to a pitch thrown without spin. But there's a big difference in vertical break: Uehara's fastball "rises" nearly a foot compared to a spinless pitch, while his splitter rises just 4-5 inches. Imagine having milliseconds to figure out whether Uehara is tossing you a tailing, high-80s fastball up in the zone, or a tailing, low-80s split that proceeds to plummet like a wasp that got whacked by a Sunday newspaper.

To help you visualize hitters' conundrum, here's a graphic showing the break and velocity of Uehara's fastball (the yellow-orange cluster on top) and his splitter (the green-blue cluster).

Pitch velocity and movement of Uehara's fastball and splitter

• Uehara has lured hitters into chasing his splitter off the plate nearly half of the time (48% chase rate), which ranks behind only St. Louis' Edward Mujica (51%) among relievers. Lefty batters would need a boat oar to reach some of the Uehara splitters that they're swinging at:

Hitters' swing rate by pitch location vs. Uehara's splitter

• Uehara has generated swings and misses 44% of the time with his splitter, highest among all relievers.
• While Uehara has registered 51 of his 87 strikeouts with his splitter, he uses his split as more than a put-away pitch. Uehara has thrown his signature offering about 37% of the time in first-pitch counts, and to great effect. Opponents are batting .143 and slugging .286 versus Uehara's first-pitch splitters.

Comments

Wonder who the Sox closer will be in '14?

Thanks very much. This is a very interesting analysis. The RS need to give him a good contract next year. Go Koji!

If he can be relied on like this for 2014 the Sox are in pretty good shape even considering Salty and Ells may be gone next year. Only a few bullpen tweaks may be needed and several of those may already be in the minors. Might make sense to get another reliable closer in case this wears on him.

The Red Sox are in great position for years to come. Our Triple A PawSox are on the verge of repeating a title, and thats without the likes of Bradley Jr, Lavarnaway, Workman, Boegarts, and other prospects that have been called up. We still have Webster, Wright, De La Rosa, Brentz, and so many other talents that are close to MLB Ready waiting in the wings.

Our High A affiliate just won the title as well. We have an amazing farm system to go with the talent we possess at the Major League level as well. we will be just fine going into next year and years after