2021 in Review: Hirokazu Sawamura’s MLB debut

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 weekday 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 Hirokazu Sawamura’s 2021 campaign.

2021 in one sentence

Hirokazu Sawamura’s first season in the majors after a career spent in the NPB began with some intriguing promise before hitting a wall, in part due to injury.

The Positives

When talking about what Sawamura brought to the table in 2021 and what the biggest reason for being excited about his near-term future in the Red Sox bullpen, it feels like you have to start with his splitter. The righty is one of those pitchers who excels largely on the back of one dominant pitch, and in this case it is indeed that splitter. With the bottom dropping out and a consistent ability to hit the bottom portion of the strike zone or just below it, Sawamura could do no wrong with the offering, helping lead to an ERA that was 33 percent better than league-average after adjusting for park effects.

Throwing that splitter just under 40 percent of the time and with an average velocity of 91 mph, he induced whiffs at a 47 percent rate and opponents came up with .237 wOBA with an expected mark actually a bit better than that. Given it was his first year in the majors there’s always a fair question of how batters will adjust in his second season and whether or not it can be as effective, but speaking strictly of this past season it was an overwhelming positive.

And that splitter was the biggest reason he was able to rack up strikeouts at an above-average rate. His 10.4 strikeouts per nine innings might be a tad inflated due to some issues we’ll discuss below, but even looking at it in percentage form his 26 percent rate is still better than average. And significantly better than average was his 35 percent whiff rate compared to a league-average rate a bit under 25 percent. Per Baseball Savant, Sawamura finished in the top five percent in all of baseball in terms of strictly missing bats.

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What was perhaps most impressive, albeit with sustainability a valid question, was the righty’s ability to perform when the pressure was the greatest. We’re talking about a split in a single-season sample size for a reliever, so this isn’t necessarily representative of some sort of true talent for Sawamura, but we’re just looking at what happened. And what happened was that he was just okay in low-leverage situations and when nobody was on base. But when the pressure started to notch up, the performance went up with it.

To that point, according to FanGraphs’ measures when he was in medium leverage situations he allowed a wOBA of .281 and in high-leverage it was at .231. Similarly, with runners on base his wOBA allowed sat at .266 and with runners in scoring position it was .231. (wOBA is on the same scale as OBP.) He induced ground balls at a high rate and was able to miss bats, so there’s some logic to it being somewhat sustainable, though it’s certainly not something to count on. But again, in 2021 he came up big when it mattered most.

The Negatives

But for all of the positives with Sawamura’s season, his peripherals were not very good, with his park-adjusted FIP coming in worse than league-average. It’s especially surprising to see considering his above-average strikeout rate, but his command was a problem all season. That led to a lot of walks as well as a lot of homers. The latter can be fluky year-to-year, making the walk rate perhaps more concerning. By the end of the season he had walked just about 14 percent of his opponents, which put him in the bottom five percent in all of baseball.

Thinking about it, these results do make sense given how much he relies on both his splitter and slider (combined to throw about 55 percent of the time), two pitches that are best thrown out of the zone. And sure enough, he hit the zone less than 39 percent of the time, 10 percentage points higher than the league-average rate. Even getting chases at a slightly above-average rate wasn’t enough to keep that walk rate in workable territory. Unless Sawamura can start inducing chases at an elite rate, it doesn’t feel like a zone rate this low is sustainable for him.

The walks were an issue all season, but they certainly started to show more in the second half, when he took a big step back overall from the first half. Prior to the All-Star break, he pitched to a 2.45 ERA while allowing a .300 wOBA. In the second half those numbers were 4.41 and .376, respectively. And the walk rate, for what it’s worth, jumped from 12 percent to 18 percent.

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Now, there are a couple of reasons for this dip from what I can see. One is that he suffered an elbow injury that kept him on the shelf for a bit and perhaps could have been affecting him all second half. Additionally, his batted ball profile changed pretty substantially, with his ground ball rate jumped from 46 percent to 64 percent. That’s notable given the state of Boston’s infield defense. Granted, his walk rate and general lack of command did enough damage on its own, but ground balls weren’t exactly ideal in front of this defense in 2021.

The Big Question

Can Hirokazu Sawamura move quickly up the depth chart?

I’m going to give this one a solid “sort of.” My blueprint for the bullpen coming into the season was only partially correct as I did not account for Garrett Whitlock being elite, so my theory was they needed someone to step up with Matt Barnes and Adam Ottavino as the number three. Clearly Sawamura was not better than Whitlock, but he was a late-inning arm for portions of this season, mostly in the first half. He wasn’t there by the end of the year and it’s hard to view him as such looking ahead to next year, but there were times he reached that point in 2021.

2022 and Beyond

Sawamura is under contract for another year in Boston, and he should very much be a part of the mix in a bullpen that is lacking in top-end talent right now. He’s going to be one of the most interesting players on the roster in my mind next season, as there is a decent case for him going in either direction. Pessimistically, the league now has a book on him and adjustments will take his splitter down a notch and his other pitches aren’t good enough to make up for it. More optimistically, he showed really interesting flashes and a little bit more polish around the zone after getting more settled in his new home isn’t out of the question. I would probably bet on him just being a fine middle reliever, but going in one direction or the other is certainly a possibility as well.

Data from Baseball Savant and FanGraphs.