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Do the Red Sox have a new Joe Kelly?

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Joe Kelly has looked much better since coming back from Pawtucket. Has he really been better, though?

David Butler II-USA TODAY Sports

There were a lot of flaws with this team’s pitching staff heading into the season, and many of them came into fruition as the year wore on. Rick Porcello’s extension seemed aggressive, and he certainly hasn’t pitched like a $20 million arm. Of course, even if you were low on him you couldn’t have expected him to be quite this bad. Many complained of the team relying too much on Clay Buchholz, and although he’s pitched well when he’s on the mound, he’s missed a significant chunk of yet another season. Justin Masterson was a worthwhile risk, but….well we know how that one turned out.

Arguably the most aggressive decision in the rotation, however, was handing a job to Joe Kelly. While he has intriguing velocity and looks like he has the potential to be at least a solid starter, he’s never been able to put it all together. As many expected to happen, he struggled mightily in the early part of the year. Kelly was so bad that he wound up spending roughly a month in Pawtucket.

Since that time, however, he’s been a much more acceptable starting pitcher. After pitching to a 5.67 ERA with a 60/31 K/BB while allowing a .756 OPS through his first 14 starts, his numbers have vastly improved since returning from Triple-A on July 22. He’s made eight starts in that time with a 3.74 ERA and 36/12 K/BB while allowing a .791 OPS. Shrinking the sample size even further, he’s had a terrific run over his last five starts. Over 32 innings in that span, Kelly is the owner of a 1.69 ERA with a 22/10 K/BB and an opponents’ OPS of .671. Looking strictly at those numbers, he’s been a different pitcher over this stretch. Is this something we can get legitimately excited about, or is this just a blip in Kelly’s odd career?

The Red Sox are on a fun run at the moment, so let’s look for some positives first. The one that jumps out the most is his improved walk rate. While he was walking 9.3 percent of his opponents before heading to Pawtucket, he’s allowed free passes to just 6.3 percent in his eight starts since coming back. On a cursory look, that’s about the only positive I can find in his numbers, unfortunately.

While Kelly’s stuff has always been intriguing, he’s never been able to put it together in a way that results in huge strikeout totals. Even during this run, he hasn’t seen anything close to a significant jump in this area. He started the year striking out 18 percent of his opponents, and that number jumped to 18.8 in his last eight starts. Even in his last five starts, the rate actually dropped to 17.6. For context here, the league-average starter in 2015 strikes out 19.3 percent of his opponents.

Overall, Kelly’s peripherals have been largely the same in the second half as they were in the first, even with the improved surface numbers. His 4.25 second-half FIP is actually a tick higher than his 4.20 FIP in the first half. The reason is a jump in home runs allowed in the second half that have cancelled out the strides he made with regard to his walk rate. Generally speaking, he’s been hit harder in the second half than in the first half. In addition to the extra home runs, opponents have a higher OPS against him since coming back from Triple-A and his hard% (which measures quality of contact on Fangraphs) has jumped from 32.6 percent to 38.3 percent in the last few months. He’s also watched his ground ball rate fall from 47 percent to 42 percent.

It’s not just the numbers we need to look at with Kelly, however. The pitch f/x data can tell us a lot as well. The one thing I’ve heard about him when people talk about this solid run of his is that he’s mixing up his pitches more of late. For a guy who supposedly has so many pitches, this would be a very positive adjustment. To his credit, it’s been mostly true. You can see for yourself, with his first-half pitch mix here, and his second-half pitch mix here.

Clearly, Kelly has a new strategy right now, as he’s thrown far fewer fastballs and sinkers in favor of his change up and slider. The shift does make some sense, as he was generating a lot of whiffs and ground balls on these pitches in the first half when they were underused. However, in the second half, both of those rates have come down. He’s had some trouble with hanging sliders, allowing more home runs with that than any other, and a .293 ISO in the second half.

Now, it’s time for my favorite part of the show: Zone Profiles. Considering Kelly’s improved walk-rate, I was expecting to see a lot more red inside the zone and a lot more blue outside of it in the second half, but that hasn’t been the case.

If anything, Kelly’s control has been even worse in the second half according to these plots. At least in the first half, he was generally keeping his ball down and in a similar area. In the second half, he’s sort of been all over the place. It was a surprising result for someone who has improved so much in terms of walks. The obvious connection to make after this would be that he’s inducing more swings on pitches out of the zone.

It doesn’t look to be an extreme difference, but there are certainly more swings at balls out of the zone in that second plot, especially on higher pitches. There are two ways to look at that. The optimists among us will say that Kelly’s stuff truly has improved and he is fooling hitters more often. The pessimists will say that, even if that’s true, major-league batters will adjust and the style isn’t sustainable.

Overall, there are more signs that this run by Kelly is smoke-and-mirrors than signs that he’s a changed pitcher, although there are some positives. He’s walking fewer batters with a style that may or may not be sustainable, and he’s mixing his repertoire up much more. However, the strikeouts are still a bit below average and he’s allowing more hard contact and fewer ground balls. It’s nice to see some of the strides that he has made lately, but at this point it’s hard to be too confident in them. Kelly still has a long way to go if he wants to carve out a starting role in the near-future.