Let's talk about Joe Kelly

At the start of the offseason, I was a little embarrassed by the fascination I had towards the Red Sox’s rotation issues. I wasn’t just curious about how they’d fill so many important holes, I needed to know how they’d do it. I spent my free time thinking of a million different ways they could do it. I know, I have no life. You learn to live with it. The thing is, now that they’ve added three new names to the mix, it’s still incredibly interesting. The talk has shifted to "How can they fill so many empty spots?" to "Is it enough, or do they need a bona fide top of the rotation guy?"

Everyone has their opinion on this issue, and we’ve had weeks to debate about what the proper move is. I think I’ve already made it clear where I stand, and I don’t plan on getting back into that today. Instead, I want to talk about something that’s stood out to me through this whole conversation. People are way into Joe Kelly. I’ve even seen arguments against getting an "ace" solely because it would knock Kelly out of the rotation. I like him as a pitcher, don’t get me wrong. I just remain curious on why people are so high on him.

We’ll start with the positives, because they are clearly there. This is a guy the Cardinals were openly upset about losing in the John Lackey deal (because teams would never lie about something like that, of course). His calling card is his ability to induce ground balls, and he's very good at it. Over his 327-1/3 career innings, Kelly boasts a career 52.4 percent ground ball rate. Among pitchers with at least 300 innings in that same span (2012-2014), only 12 have a higher rate.* While it’s not everything, inducing ground balls at that kind of rate can go a long way towards success. What makes Kelly so fascinating is that he pairs that ground ball ability with velocity. In the last ten years, he is one of four starting pitchers to pair a 50+ percent ground ball rate with a fastball velocity of at least 94 MPH. When you consider that kind of tantalizing package with the fact that he will be just 27 next year, it’s easy to get excited. Still, with all of that being said, there are things working against him, as well.

*Justin Masterson is one of them, and Porcello is one spot behind Kelly

Chief among Kelly’s issues are his peripherals, which aren’t nearly as impressive as one would expect from someone with his profile. Despite the high velocity, his strikeout numbers are fairly pedestrian. While the league-average pitcher has hovered around a 20 percent K-rate since 2012, Kelly’s career rate is just 15.7. He’s the only pitcher with such a low K-rate in that span that throws at least 94 MPH. This would all be fine if he had impeccable control, but he does not. This is not to say he is bad in this area, but merely average. The total package ends up underwhelming, though. Of the 131 pitchers with at least 300 innings since 2012, all but five have a better K/BB ratio than Kelly’s 1.80. Even with his good-not-great home run rate put into the mix, he comes out with an underwhelming FIP, worse than 70 percent of those same 131 pitchers. Of course, FIP is far from a complete pitcher of what a pitcher is, but it’s certainly part of the story. And this part of Kelly’s story indicates a serviceable back-of-the-rotation arm, but not someone you build a unit around.

This is why I find it so confusing that people are so against him going to the bullpen in the event another, demonstrably better arm is brought in. To me, he is the clear starter to move in this case. Rick Porcello is coming off the best season of his career and has a proven track record of a durable starting pitcher in his career. Wade Miley also has that durable track record on top of significantly better peripherals, especially with the gains he made in strikeouts in 2014. Clay Buchholz has shown the ability to be an ace at the major-league level as recently as 2013, something Kelly cannot claim. One could make a reasonable argument that Justin Masterson should get the rotation boot before Kelly, but that would ignore the fact that he signed a one year deal to rebuild his value. That deal almost certainly included assurances he would be in the Opening Day rotation.

In addition to others having more of a claim to the rotation, Kelly has more of a claim to the bullpen. He’s had experience in both roles, and his stuff has appeared to play up as a reliever. Most notably, his strikeouts are way up, going from 14.5 percent as a starter to 21.5 percent out of the pen. His K/BB ratio jumps from 1.58 to 3.50. It should be noted, of course, that there are sample size issues at play. Even beyond the starter/reliever splits, he’s had some issues against left-handed batters. When the opponent has the platoon advantage, his OPS allowed is almost 100 points higher than when he holds the advantage, and the K/BB ratio falls from 2.4 vs. RHB to 1.3 against lefties. This is easier to hide in the bullpen.

There’s been a lot of love for Joe Kelly this offseason, and some of it is warranted. He’s a fine pitcher with an interesting skillset who can look like a very good one when he’s on his game. However, there isn’t much reason to project him as too much more than a back-end starter for 2015. There are many reasons for the Red Sox to acquire another starter, and there are plenty of reasons for them to stand pat. Whatever they decide, though, Kelly shouldn’t really be a big factor in the decision.

**Stats from Fangraphs and Baseball-Reference