An In-Depth Look at Martín Pérez


The Red Sox and Martín Pérez agreed to a reunion this Saturday, ensuring another fun year of #PérezDay for Fenway faithful.  Pérez makes another member of the Boston rotation with plenty of question marks, but should be able to prove himself worth the $4.5 million he's due this season (plus incentives for throwing 170 or more innings).  To better understand the pitcher we're getting, let's take a look at his 62 innings from 2020, and look at changes between 2019 and his first season with Boston in 2020.  

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Surface Stats

Pérez posted a 4.50 ERA and 1.34 WHIP in his 12 starts last season, backed by a 4.88 FIP and a 5.20 xFIP.  As expected, he was below average in K% with a 17.6 and also walked too many hitters with a career-worst 10.7 BB%.  Despite those poor K and BB ratios, he was a pleasant surprise for many Sox fans (myself included).  Part of his success can be credited to a low .266 BABIP, which seems a bit unsustainable.  Despite his blemishes, this level of production should suffice for a back-end of the rotation guy.  Bloom and company will need to find another capable starter or two for Pérez to serve his proper role as number 4 or 5 in the rotation.  

Digging Deeper

One stat that jumps out at you when looking at Pérez's 2020 is his groundball rate.  Pérez comes close to being a groundball pitcher, with a 49.9 career GB%.  This was not the case in 2020 as that number decreased to a 38.5 GB%, nearly a 10% decrease from 2019.  Luckily for Martín, his increase in fly balls did not lead to an increase in home runs.  That makes sense when looking at the statcast numbers on Pérez, as he was among the top pitchers in limiting exit velocity and hard hit % for the second consecutive season.  Other than these numbers, the changes of note in Pérez's statcast, batted ball, and plate discipline data include regression in xwOBA, xSLG, xISO, and barrel % allowed.  Hopefully we can see him at least get back to his norm in those areas.


The new cutter was THE topic of discussion when Boston signed Pérez last offseason, though its usage remained almost exactly the same in the first season with pitching coach Dave Bush.  After throwing cutters 30.8% of the time in '19, we saw them thrown for 32% of pitches in 2020.  Pérez also slightly increased his changeup and curveball usage while decreasing sinker usage by roughly 7% (likely a factor in the decrease in groundballs).  In year 2 with Bush and year 1 with Alex Cora, I'd like to see the changeup usage bumped up a little more and perhaps some more sinkers with less four seam fastballs. The change seems to be the one pitch where Pérez generates a decent amount of whiffs (32.2 whiff % was the highest of any pitch for him in 2020 by 8%), while sinkers should help him force more groundballs if he wants to get back to that style of pitching.  

2021 Outlook

Regardless of how this season goes, Pérez remains one of the many intriguing arms in Boston and it'll be interesting to monitor how his repertoire is utilized. This is a very low-risk contract due to the small cost, though the ceiling isn't anything spectacular.  The Steamer projections via Fangraphs currently have Pérez down for 134 innings, a 4.90 ERA, and a 1.49 WHIP in 2021.  Expect him to eat lots of innings while allowing plenty of hits and walks, but not many back-breaking home runs.  If we can add a couple better arms and get a repeat of 2020 from Pérez as the number 5 starter, it should be looked at as a nice little win for the Bloom regime.

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Boston Sports Syndicate: An In-Depth Look at Martín Pérez
An In-Depth Look at Martín Pérez
Boston Sports Syndicate
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