One Big Question: Can Matt Strahm get his strikeouts to his pre-injury levels?

Welcome to the annual Over The Monster One Big Question season preview series. Over the next 40(ish) days, we will be running through every player on the Boston Red Sox 40-man roster and identifying a key question for them pertaining to the coming season. We will go through the roster in alphabetical order. For the most part, these will run Monday through Friday every week running up to the week before Opening Day, at least as things are scheduled right now. Obviously, the lockout may change the timing of the season, and it also means we will likely see more additions of new faces. If need be, we will add some weekend posts to fit any and all additions to the 40-man before Opening Day. You can catch up with every post by following this link. With that, today we cover Matt Strahm.

The Question: Can Matt Strahm start missing bats again?

Heading into the other side of the lockout and the frenzy of transactions everyone was expecting, and eventually came to fruition, it was clear that one of the objectives for the Red Sox should be to bolster their bullpen. There was upside in the group, but enough questions that reinforcements needed to come in at some point. They didn’t make the big splash in that area some were looking for, but they did add two left-handed arms, both of whom we’ll look at in our One Big Question series this week. First up is the first guy they signed, Matt Strahm.

It wasn’t all that long ago that Strahm was considered one of the most intriguing up-and-coming left-handed arms in the game. The southpaw originally came up through the Royals system after being selected as a 21st round pick and made his major-league debut in the middle of last decade, which also happens to be when the Royals were making back-to-back trips to the World Series in large part because of a strong ability to build bullpens. He eventually landed with the Padres for the 2018 season, when he pitched in a swingman kind of role and finished with a 2.05 ERA and a 3.36 FIP over 61 ¹⁄₃ innings.

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Unfortunately, injury has hampered his development since then, and since the end of 2019 he’s only made 25 appearances for a total of 27 ¹⁄₃ innings. On the one hand, it’s hard to take too much away from numbers in that kind of sample just in general, and perhaps even more so when those innings are coming off significant injury, mostly with his knee. With that said, though, it’s the only sample over two years we have for Strahm, and looking at those numbers the thing that is most clear to me is that he is no longer missing bats like he did when he was first breaking out with the Padres.

Back in the mid-2010s, one of the reasons Strahm’s numbers were so good and why many around the league pegged him as a potential breakout for a few years straight was his ability to miss bats. The southpaw struck out at least a batter per inning in each of the first four years of his major-league career, taking him through 2019, with a percentage rate of at least 24 percent in each year as well. However, over the last two seasons that rate has stuck under 20 percent, which is fairly significantly below average in this era of baseball. Now, to be fair, Strahm’s control has tightened up significantly and he’s inducing a few more ground balls to try and limit damage on balls in play, but with this move the Red Sox were seemingly buying upside for cheap. With Strahm, the upside is most likely to be reached if he misses bats at a high rate again.

To me, a lot of this conversation with his strikeout rate comes down to the effectiveness and usage of his slider. Looking back at 2018 and 2019, the two years he looked closest to breaking out (his overall numbers in 2019 aren’t all that great, but the strikeout and walk numbers were), it was the slider that did the most damage in racking up the strikeouts. In 2018, for example, the pitch induced whiffs on an astonishing 55 percent of swings. He came back down to Earth a bit in 2019, but even then it was still a very solid 27 percent whiff rate. It was far and away his most effective secondary along with his fastball. The last two years, however, the whiff rate was hovering in the 15 percent range, a significant drop. And in 2020, it suddenly became his fourth most used pitched as opposed to second like most of the rest of his career.

Now, in fairness last season he got back to using it as his second pitch again, albeit in a tiny six-inning sample. But the whiff rates were still lacking, and there are two issues to which I’d point. One has to do with where he was throwing the pitch. We know that the most effective breaking balls in today’s game are down in the zone and typically off the plate on chase swings. If you look at where he threw the pitch in 2018, you can see that is exactly what he was going for most of the time. If you look at 2020 and 2021, though — below only 2021 is pictured, but 2020 is the same story — a lot of those sliders were right out over the plate, which in turn makes it a lot easier to get wood on the pitch.

Now, again, the samples with which we’re dealing are extremely small, and especially coming off injury it is not a surefire measure of future performance. On the other hand, it’s a troubling trend. I would add to it a change in the slider’s profile which also seems to be playing into this. Back in 2018, per Baseball Savant, Strahm’s slider moved on average 6.2 inches horizontally, well more than league-average. One can imagine this kind of sweeping slider can induce a ton of swings even when it finishes off the plate. After that, though, it’s become a much tighter pitch. I haven’t been able to see if that’s on purpose or not, but my guess is it was done to reduce his walk rate, which was a bit out of control early in his career. The last few seasons that rate has been much better than average.

Ideally, there is a balance here that can be struck, where his slider is still sweeping enough to get whiffs but not so much that batters can spit on it when they pick up the spin, leading to high walk rates. That, of course, is easier said than done, however. If a choice has to be made, I would divert back to that old style with whiffs and walks. When Strahm first made the change to tighter sliders, he was trying to break in as a starter where those control issues are more likely to bite him. With this Red Sox team, he should be viewed as a pure reliever, and Boston needs some of those guys to step up. There is clear risk, but for Strahm to take the leap forward the Red Sox are looking for the clearest way to me is simply leaning into today’s game and get back to that big sweeping slider, living with the extra walks that may emerge from its wake.

Statistics in this post from FanGraphs and Baseball Savant.