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Clay Buchholz needs to improve with runners on base

Nothing about the start of Clay Buchholz's season has been good, but he's been particularly bad after he's allowed runners to reach base.

Mark L. Baer-USA TODAY Sports

There’s no way to sugarcoat the start of Clay Buchholz’s season. He’s been straight-up bad. Through his first four starts — which have totaled 21-1/3 innings — the right-hander has a 6.33 ERA to go along with a 5.46 FIP. For context, those are extremely not good. I’m not going to say that he’ll certainly right the ship, nor will I say that he’s doomed for failure through the rest of 2016. The reality is, I have no idea what to think about any given Buchholz start at any given moment in time. However, as I look through some of his early-season numbers, one thing in particular has stood out to me. He has struggled mightily with runners on base.

Split Batters Faced K% BB% wOBA
Bases Empty 53 22.6% 13.2% .312
Runners on 41 12.2% 4.9% .433

Above, you can see just how stark the difference has been after Buchholz has allowed a runner to reach base. A few things stand out from these numbers. For one thing, while the walks are way down, the strikeouts are as well. Intuitively, this seemed pretty normal to me, but the league averages show no discernible difference between the two situations. On the one hand, his K/BB ratio is actually much better with runners on base, which seems like a good thing. However, his K%-BB% is actually worse, and there are studies that say the latter is the better measure of performance. On top of that, the overall production has been much worse with runners on base, as illustrated by that massively inflated wOBA. For a little bit of context, a .433 wOBA would’ve been the second best mark in the majors last year, while .312 would’ve been right inside the top-100, one slot above Billy Butler. For what it’s worth, Buchholz had this problem last year, albeit to a smaller degree allowing a .272 wOBA with empty bases and a .323 mark with runners on base. Over his career, there’s been essentially no difference with a .309 mark compared to a .314.

The biggest issue here has been the amount of power opponents have been able to generate when they’ve had runners on base against Buchholz. All of the home runs he’s allowed in 2016 have come in these situations, as well as three of the four doubles. To put it simply, batters are seeing him a lot better and are crushing the ball. His ground ball rate is falling by ten percentage points down to 33 percent with runners on, while his fly ball rate is climbing by 20 percentage points to 51 percent. On top of that, he’s allowed a more pull-happy approach with his opposite field percentage falling by nine points down to 12 percent. Obviously, that is all quite bad.

I wanted to investigate this a little closer to see if I could find any subtle differences between the two splits. To do so, I went over to Baseball Savant to check out some Pitch F/X data. The first thing I looked for was repertoire changes. While the changes weren’t massive, Buchholz has mixed things up when he’s pitched out of the stretch. To put it simply, he’s throwing his four-seam fastball more while shying away from his curveball. Intuitively, this makes sense. There are already runners on base, so he relies on his fastball to get more strikes and avoid allowing any free passes. The flip side, of course, is that it also makes it much easier to connect for hard contact.

The thing is, Buchholz hasn’t really gotten any fewer balls called nor any more called strikes. All that’s happened is he’s generated far fewer whiffs, and in turn has allowed a lot more balls in play. Below is a side-by-side of his events breakdown from each split, with the "bases empty" on the left and the "runners on base" on the right.

Obviously, I couldn’t do this exercise without checking out the zone profile. Sure enough, there are some discouraging changes once Buchholz allows runners on base. Below is another side-by-side comparisons with the splits on the same side as the picture above.

A couple things stand out to me here. First of all, he’s favoring his arm-side more. To wit, he’s throwing to that side (counting the left side of the zone as well as balls on that side of the plate) 43 percent of the time with the bases empty and 50 percent of the time with runners on base. On top of that, he’s missing in the middle part of the plate far too much. Counting just the pitches in the middle vertical third of those zone profiles, Buchholz is hitting the middle of the plate 9.5 percent of the time with the bases empty and 18 percent of the time with runners on base. That, combined with the more conservative, fastball-heavy approach with runners on is what’s contributing to those huge power numbers.

As Joon said just last week, the Red Sox could really use an effective Clay Buchholz moving forward. With the rotation as a whole struggling, they could use an arm to step up, and there’s no doubt he has that potential. If he’s going to bounce back, he’ll need to do better after he allows base runners. I wish I could say whether this was a matter of him pressing or a mechanical oddity out of the stretch, but the truth is I’m not sure. There’s no point in speculating. All I can tell is that something is wrong based on these numbers. It’s always possible to chalk it up as bad luck, but that seems overly simplistic in this case. Whatever it is, Buchholz and the coaching staff need to figure out what is ailing him with runners on base if he is going to right the ship in 2016.