Joe Kelly

What Do the Red Sox Really Have in Joe Kelly?

The Red Sox began the season with a rotation full of question marks, and no starter looked like less of a sure thing than Joe Kelly.

After arriving in Boston prior to last July’s trade deadline, Kelly gave the Red Sox 10 middling starts, showing some intriguing mid-90s velocity but little else. Despite playing a part in the Cardinals’ run to the 2013 World Series, Kelly proved to be expendable in St. Louis’ eyes, and many questioned the Red Sox’s intentions to hand the right-hander a full-time spot in their rotation.

At the time, John Farrell pinpointed Kelly’s lack of any notable secondary pitches as the biggest obstacle standing between the young hurler and a starter’s role. The goal for Kelly and the Red Sox, then, seemed clear: Develop an effective offspeed pitch or two to pair with his overpowering sinker.

Kelly showed little sign of any new or improved offering this spring, and after he left a March 16 outing with biceps tightness, his readiness for the beginning of the season looked in doubt.

Of course, none of this stopped Kelly from making his first scheduled start anyways, with the righty twirling a one-run, seven-inning gem against the Yankees in the Bronx. Kelly followed that up with a solid effort against the Orioles in which he earned a no-decision but kept the Red Sox in the game.

Wednesday night against the Rays, Kelly again impressed for the better part of five innings before the wheels fell off in an ugly sixth. Kelly’s struggles in the frame served to emphasize that two strong outings do not mean he is suddenly a dependable major league starter.

Kelly’s struggles on Wednesday served to emphasize that two strong outings do not mean he is suddenly a dependable major league starter.

Still, there has been one intriguing development in his arsenal (especially in the context of Farrell’s comments last year) that’s paid dividends when he’s been successful this season.

Kelly has begun using a slider as his main secondary offering, and the pitch has yielded great success early in 2015. As Rob Bradford wrote at, Kelly threw the pitch in college but only recently began using the slider again in the weeks leading up to his first start against New York.

There is little denying how impressive Kelly’s slider looked in his first start against the Yankees. He threw the pitch 18 times, according to Brooks Baseball, and garnered 11 swings and eight whiffs with the offering. Given how little he has depended on the slider in recent seasons, the comfort Kelly had in using it as a put-away pitch was remarkable.

Kelly’s reliance on his slider continued into past two starts, and through 17.2 innings this year, the 26-year-old has turned to his slider 15.4% of the time after barely using it a season ago. (There is a chance, given Kelly’s comments to Bradford that he hadn’t thrown his slider since college, that Pitchf/x was incorrectly labeling some of his pitches as sliders in 2014.)

In terms of location, Kelly’s objective with the slider has been clear—bury it down below the strike zone. The results have followed, with Kelly generating whiffs 47% of the time for every swing at his slider, per Brooks Baseball. Long a pitcher who struggled to strike batters out, Kelly’s strikeout rate has risen to 25% as a result, far above his career average and the type of performance projection systems were expecting from him this season.

The reality that Kelly has made just three starts this year is the important caveat in all this. How quickly things unraveled for him in Boston’s loss Wednesday provided a harsh reminder that he hasn’t suddenly solved all his problems overnight.

Nevertheless, that Kelly has found what looks to be a viable breaking ball and an ability to strike batters out with greater frequency is certainly good news for the Red Sox. Farrell and the rest of Boston’s staff made no secret that Kelly needed to develop other quality pitches along with his fastball, and this slider looks like a great place to start. Even in Wednesday’s outing, Kelly finished with seven strikeouts to just one walk, and his only free pass came against the final batter he faced. Those types of numbers indicate there is further potential here that Kelly is beginning to tap into.

In addition, it’s worth noting that Kelly has increased his four-seamer usage so far in 2015. He is still turning to his sinker in 46% of his offerings, but that mark is noticeably below the 58% frequency with which he threw the pitch between 2013 and 2014 with the Cardinals. Given Kelly’s command problems in the past and how volatile sinkers can be, it’s fair to wonder if the Red Sox have encouraged Kelly to throw his four-seamer more often to help curb his walk issues.

With what looks to be a legitimate slider and elite fastball velocity, Kelly is making genuine progress toward becoming a starter the Red Sox can depend on.

This increased reliance on his four-seamer doesn’t mean Kelly’s inconsistent control is a thing of the past, of course. His early-season success with the slider could similarly prove to be an April blip rather than a sign of things to come.

Yet Kelly is clearly working to make changes to his repertoire and the way he attacks hitters. His slider has gotten real, encouraging results against major league batters, and it’s worth noting that Kelly’s average fastball velocity is the second highest of any starter in baseball through Wednesday (min. 50 pitches) behind only Yordano Ventura.

That’s not the type of ability you can teach or develop, and Kelly’s big arm is the main reason why the Red Sox traded for him last July. Kelly isn’t likely to fulfill that Cy Young prediction he made this offseason, and he isn’t suddenly going to become the “ace” of Boston’s staff. But with what looks to be a legitimate slider and elite fastball velocity, Kelly is making genuine progress toward becoming a starter the Red Sox can depend on.

Photo by Keith Allison.

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