Red Sox Sign Koji Uehara

The Red Sox have found their seventh inning man. The club signed 38-year-old right-hander Koji Uehara to a one-year deal with a $4.25 million base salary Thursday.

Boston’s bullpen struggled last season from Andrew Bailey’s injury to the early implosion of Mark Melancon to the eventual meltdown of Alfredo Aceves. The club finished in the league’s bottom half in both ERA (3.88) and FIP (3.91). Uehara is one of the best control pitchers in the big leagues and he can generate swings and misses. Should Andrew Bailey struggle to get on the field again, the Red Sox have a player they can trust in the later innings in Uehara.

Uehara lives on his control. He doesn’t have blow-em-away stuff, but all of his pitches have incredible movement. His fastball rarely breaks 90 but has heavy late arm-side run. His cutter gives him a change-of-pace option against lefties, and the splitter is the out pitch. All are routinely thrown for strikes — even the splitfinger is only a ball 36 percent of the time, roughly the average for the major league fastball. Uehara works almost exclusively in pitchers’ counts as a result — he didn’t pass through a single 3-0 count in 2012 and he threw just 25 pitches with three balls out of 513 total pitches.

When Uehara gets in these deep counts, he unleashes the splitfinger. It’s a devastating pitch when spotted well — buried in the lower half of the strike zone or below it can rack up the swings-and-misses, and that’s exactly what Uehara does with it:

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The splitter is an incredible effective pitch, drawing constant swings (59 percent) and whiffs (39 percent of swings, 23 percent of total pitches). It’s the driver behind Uehara’s sharp 9.82 career strikeout rate (10.75 in 2012). His control with it allows him to finish pitcher’s counts instead issuing walks as he tries to nibble around the zone or being forced back into the fastball in a full count.

As good as the movement makes his fastball, its lack of velocity is an apparent weakness at times. When hitters make contact with it, they’re able to make it hurt — of 357 at-bats ending on a Uehara fastball, 24 (6.7 percent) are home runs. Hitters have a .527 slugging percentage on contact against it. Uehara’s good at avoiding in-play contact with it — 14.1 percent against a league average of 19.3 — but MLB hitters are too good to let even the sneakiest fastball by too often.

But Uehara’s lack of velocity merely lowers his ceiling from baseball’s best reliever to perhaps its best setup man, capable of posting ERAs and FIPs under 3.00 year-in and year-out. He’s going to rack up the strikeouts and limit walks with his deadly fastball-splitter combination, limiting the damage on the inevitable home runs.

The Red Sox should be happy with their investment — Uehara offers stability and quality in the bullpen, two aspects last year’s club sorely lacked.