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Analysis: What Can We Expect from Joe Kelly as a Reliever?

This week the Cards announced that Jaime Garcia will be returning from the DL and starting on Sunday, pushing Joe Kelly out of the rotation and into the bullpen. Kelly has been solid so far this year filling in as a starter while Garcia and Chris Carpenter have missed time due to injury.

Kelly is somewhat of an enigma as a pitcher with elite fastball velocity who has outcomes more resembling a sinker-baller. Kelly’s fastball has averaged roughly 93-94 MPH this year, which is good for 13th among starters with at least 60 innings pitched. Kelly’s 5.9 K/9, however, ranks 27th among the 31 pitchers with an average fastball velocity above 92.5 MPH and is a full strikeout below average overall for starters. On the other hand, Kelly’s 51% GB rate ranks 7th among the same group of hard throwing starters and a remarkable amount of those groundballs come on his fastball.

Looking deeper at this group of 31 high velocity starters, Kelly is one of only 10 pitchers that do not feature a hard slider above 84 MPH. A few of these pitchers (i.e. Yu Darvish and Ubaldo Jimenez) do feature a slider that is in the 80-82 MPH range along with a slower curveball, but most are like Kelly and throw a slurvish breaking ball or true curveball. This smaller list includes pitchers like Stephen Strasburg, Matt Moore, and Gio Gonzalez with exceptionally low contact rates on both their fastballs and breaking balls and correspondingly high K/9. More importantly, Kelly’s 89.9% contact rate against the fastball and 73% contact rate against the curveball each stand out as second highest on the list only to Ubaldo Jimenez—who has been less than impressive this year.

Joe Kelly has elite velocity, but his lack of deception and mediocre breaking ball do not generate the number of strikeouts customary for a pitcher with this velocity. Kelly’s ability to keep the ball on the ground and out of the stands, however, has made him valuable and successful as a starter. Moving to the bullpen, we can expect Kelly’s velocity to increase, as 14 of the 17 pitchers in the last 3 years with at least 60 innings as a starter and 20 innings as a reliever had a higher average fastball velocity out of the pen. It’s not clear, though, that this increase in velocity will generate the subsequent increase in strikeouts for Kelly that is normally associated with increased velocity.

Kelly’s unique repertoire and pitch outcomes make it hard to find a suitably comparable pitcher that has thrown significant innings as both a reliever and starter in the same season. On one hand, pitchers like Brian Duensing, Brad Bergesen, and Craig Stammen have similar K, BB, and GB rates, but they feature a very different, sinker-heavy repertoire. Alfredo Simon and Manny Parra are both hard throwers that have recently started and relieved in the same season, but Parra is erratic with much higher BB and K rates and Simon transitioned the opposite direction, going from reliever to starter.

            The best comparison may be last night’s starter for the Nationals, Ross Detwiler, who joins Kelly in the bottom five in K/9 of the pitchers this year with average fastball velocities above 92.5 MPH. Detwiler has an average K rate and high GB rate working both out of the pen and rotation this season. It’s hard to draw real conclusions for Detwiler based on only 13 innings as a reliever this year, though, and as a lefty his similar repertoire still plays much differently than Kelly’s from the right side.

Realistically, we should expect Kelly to perform similarly out of the pen as he has in the rotation. He will throw a decent amount of strikes and keep the ball on the ground, but his plus velocity will probably not translate into high K rates and subsequently he will be less valuable in high leverage situations. The only subtle caveat to this projection is the possibility that Kelly deliberately pitches to contact because of his high GB rate in order to keep his pitch count down, in which case he may be able to generate more strikeouts as a reliever in situations with runners on base. I wouldn’t hold my breath waiting for this to happen, though.

Perhaps the most important factor for Kelly’s performance out of the pen will be how long his relief stints last and how many lefties he faces. As the Fangraphs PITCHf/x heatmaps of Kelly’s curveball location against lefties and righties below show, without a hard slider to throw to a lefty’s back foot, Kelly is predominantly fastball-changeup to lefties. The result is a .371 to .293 wOBA split against lefties and righties, respectively. Translation: don’t expect Kelly to fare too well in long relief appearances against a lefty heavy lineup.

 

 

 

 

 

 

 

 

The return of Jaime Garcia should be a great boost to an already solid Cards rotation. More importantly, it will allow Joe Kelly to aid the mid-inning relief corps—providing a certain upgrade over the likes of Trevor Rosenthal, Barrett Browning, and Fernando Salas. Kelly will keep the ball in the yard and be effective against righties, but don’t expect a move to the pen to bolster his strikeouts. Just throwing 95 doesn’t turn you into a Jason Motte-esque high leverage strikeout machine…Kelly has already shown that this year in his performance as a starter.

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