2021 in Review: Martín Pérez had his moments, but eventually faded

Welcome to our 2021 Boston Red Sox in Review series. This is, as you can probably guess, where we will be reviewing all of the players who made at least a modest impact on the Red Sox in 2021. Every week day we’ll be deep diving into one player, describing the season in a sentence, looking at the positives from the year as well as negatives, looking back at our one big question from our season preview and looking ahead to the 2022 season. Today we look at the year that was for Martín Pérez.

2021 in one sentence

Martín Pérez had his moments in the first half as a starter, but ultimately couldn’t hold that role and was relegated to long relief duty.

The Positives

When Pérez was first brought to the Red Sox prior to the 2020 season, many pointed at the contact he allowed as a reason for optimism, while the pessimists among us pointed to the lack of strike zone control he had. The southpaw struggled to miss bats while also issuing more than his share of walks, and in today’s era of baseball it is extremely difficult to succeed with that kind of skillset. So that’s why it was nice to see, amid all of the other struggles, that Pérez was able to improve both his strikeout and walk rates this season. Pérez finished 2021 with a strikeout rate just over 19 percent, which was the highest rate of his career (though still pretty significantly worse than league-average) along with a walk rate just over seven percent, his lowest since 2015. Relative to the league those are still pedestrian at best, but it was a step in the right direction for him in perhaps the most important area for a pitcher.

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And we especially saw the fruits of these improvements in May. We have a tendency to forget the first half given how much is packed in a second half and postseason run, but there was a stretch where Pérez legitimately played a massive role on this roster. Over a seven-start stretch from the end of April through early June, the lefty pitched to a 1.98 ERA over 41 innings, striking out 37 and walking nine. The Red Sox really separated themselves in the standings in that first half of the season, and Pérez played a big role in it. While things went downhill later, as we’ll get to, they don’t get to where they end up without that first half, and by extension without Pérez having this dominant stretch.

And then beyond those two points, there are another couple of minor positives to look at from his 2021. To start with, he brought his sinker back as a prominent pitch after using it a bit less in 2020, and it was a good decision. He hardly missed any bats with the offering, but it induced a ton of weak contact, and most of it on the ground where any possible damage would be limited. Additionally, he had a solid year against fellow lefties, allowing a .296 wOBA. That success allowed him to keep a role in the bullpen even after pitching himself out of the rotation.

The Negatives

We kicked off the previous section talking about Pérez’s ability to induce weak contact being a reason some were optimistic about his prospects at the start of his Red Sox career. And while he was able to improve on the strikeout and walk fronts, the quality of contact was just not there and he finally started to give up some hard contact which led to his ultimately downfall and exit from the rotation in the summer. According to data from Baseball Savant, Pérez ended the season in the bottom quarter of the league in each of the following categories: Expected wOBA, expected ERA, expected batting average, expected slugging, hard-hit rate, and barrel rate. He was in the bottom 10 percent in each of the first three of those. When that kind of contact is combined with a strikeout rate that, while improved, still sits towards the bottom of the league in its own right, disaster is inevitable.

The big reason for that surge in hard contact is that his trusty cutter started to betray him. This was the pitch that was always credited with his turnaround in Minnesota, at least in terms of that quality of contact. He added it to his repertoire and almost immediately started allowing some of the weakest contact in baseball. The magic wore out in 2021, though, as batters finished the year with a wOBA (and expected wOBA) over .400 against the pitch, which is terrible. The average exit velocity against the cutter came in at 90 mph compared to 85 mph or lower in each of the previous two seasons since its implementation.

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All of that led to the summer swoon for Pérez when he ultimately lost his rotation job. The magic started to wear off almost immediately in June, with his second start really being the beginning of the end. His first start that month was a masterpiece in which he tossed 7 ²⁄₃ shutout innings against the Astros. He allowed six runs in two innings the next time out, and starting there he pitched to a 7.13 ERA until he was moved to a long relief role in early August.

The Big Question

Can Martín Pérez sustain his 2020 success model?

This is in reference to that aforementioned weak contact model that helped spark some optimism. As we’ve discussed plenty, it was not sustained into 2021 and eventually kicked him out of a starting role altogether.

2022 and Beyond

Pérez seems exactly like the kind of pitcher who will be signed either right at the start of camp or shortly after it begins, and likely on a minor-league deal with a spring training invite. He’s been too reliable in terms of health and too good of a clubhouse presence to be ignored entirely, but ultimately the performance hasn’t been good enough to justify a guaranteed 40-man spot. I think he’ll ultimately make someone’s roster this year and hang on for a little while longer, but I think his time in Boston is likely done.