Seven years between big league appearances, this flame-thrower is a different pitcher

When the Red Sox signed Tyron Guerrero to a Minor League contract in January, the move didn’t exactly cause a stir.

But a small group of fans may have remembered a time when Guerrero did cause a stir. The 6-foot-8 right-hander logged 112 appearances for the Marlins from 2018-19, and while he wasn’t all that good -- he pitched to a 5.80 ERA -- he was nonetheless remarkable. That’s because Guerrero threw exceptionally hard at a time when premium velocity was not yet taken for granted the way it is now, between the Jacob Misiorowskis and Mason Millers of the world. In that two-year span, Guerrero actually threw more pitches 100+ mph than Aroldis Chapman. He wasn’t brilliant, but he was awesome, and unequivocally an early Statcast darling.

It's hard to believe, but that is the same Guerrero who, at age 35, has become a lethal weapon in Boston’s bullpen. He has a 2.49 ERA in 21 2/3 innings and has been unscored upon in 17 of his 21 appearances. He's moved up the pecking order, too, pitching his way into a leverage role -- and the surging Red Sox have won each of the last seven games that Guerrero has pitched in.

A seven-year odyssey between big league appearances included three tours abroad (two in Japan, one in Mexico) and even a name change -- he goes by Tyron now, not Tayron, citing a clerical error for the former. He is a completely different pitcher now, too, and not just because he's getting results.

The main difference is that Guerrero has gone from walking the world to walking absolutely no one. His 13.6% walk rate from 2018-19 was fifth highest among 316 pitchers to throw at least 100 innings in that span. This year, he has issued just two free passes in 21 2/3 innings. That's a 2.2% walk rate, which is the lowest among 429 pitchers to throw at least 20 innings.

That's an incredible turnaround and, at the same time, it's easy to see why Guerrero stopped walking people: No one is pounding the zone at a higher clip than Guerrero. Among 461 pitchers to throw at least 300 pitches this season, Guerrero is the only pitcher with a zone rate above 60% -- he's at 60.5% -- and no one is even close to him. (Logan Henderson of the Brewers is second on the list with a 57.3% zone rate.)

This is historic. In the pitch-tracking era (since 2008), only three pitchers have finished a season throwing pitches in the zone more than 60% of the time.

Highest single-season zone rate, pitch-tracking era
Min. 300 pitches

1. Rich Hill (BOS), 2015: 61.5%
2. Jake McGee (LAD), 2020: 60.8%
3. Tyler Rogers (SF/NYM), 2025: 60.6%
4. Tyron Guerrero (BOS), 2026: 60.5%

“The thing coming in, based on his last sint up in the big leagues, was like, ‘Will he throw enough strikes?’” Red Sox interim manager Chad Tracy said last month. “All he did in Spring Training all the way through the Minor League season, he just kept throwing strikes. And you’re like, ‘Is he gonna keep staying in the zone like that?’ And he did it in Worcester, and he’s doing it here.

“But when he’s around the zone, which he has been for the better part of two-plus months now since Spring Training, and he’s throwing 103 miles an hour, it’s hard to hit.”

That is the other part to all of this. You can’t come in the zone that often and be successful without good stuff, and Guerrero is filthy. His arsenal grades out at 111 Stuff+, an all-encompassing metric that attempts to grade pitches on things like movement, velocity, etc. That number is the fourth best on Boston’s pitching staff behind Chapman, Payton Tolle and Garrett Crochet. Pretty good company.

Bear with us, because things are going to get even weirder. Although Guerrero wields a three-pitch mix, he is as close as there is to a one-pitch pitcher in the game today. Guerrero throws his sinker -- which averages 100.0 mph -- a whopping 84% of the time. Among pitchers to throw at least 300 pitches this season, only Kenley Jansen uses a single pitch more often than Guerrero does with his sinker. And Jansen has made an entire career out of his signature cutter, which may very well take him to the Hall of Fame.

Remarkably, as you can see below, Guerrero didn't even throw a sinker in his first go-around in the Majors, instead relying on a four-seam fastball.

These days, even hard-throwing relief pitchers are varying their arsenals and throwing fewer fastballs, emulating starting pitchers. Not Guerrero. This is different than Tommy Kahnle bedeviling hitters with his changeup. Guerrero is overwhelming hitters, not fooling them.

So, how can a pitcher be successful while throwing a single pitch type so often? Well, it helps to be unique.

The average right-handed pitcher releases the baseball 6.5 feet in front of the pitching rubber. Thanks in part to his 6-foot-8 frame, Guerrero strides further down the mound, releasing the ball 7.1 ft. in front of the rubber, on average. Those additional eight inches mean that the hitter has even less time to react to the pitch.

On top of that, Guerrero's sinker bores into the plate at 99.9 mph. Only six pitches (min. 100 pitches thrown) are thrown at a faster average velocity, and only the Dodgers' Edgardo Henríquez throws a harder sinker. Combine premium velocity with elite extension, and you get a pitch that is incredibly difficult to hit, let alone square up.

In Guerrero, we have a pitcher with filthy stuff pounding the zone, and if you put those two facts together, this next stat shouldn’t be all that surprising. Guerrero is consistently getting ahead of hitters. He's thrown 38.9% of his total pitches when he is ahead in the count; in the first three years of his career, that number was 27.6%. Only the Astros' Josh Hader and the Braves' Raisel Iglesias throws a higher rate of pitches when ahead in the count. That is tremendous count leverage, which is one of those topics that everyone is talking about these days.

Add it all up, and that's how the 35-year-old Guerrero reinvented himself as a legitimate weapon for the surging Red Sox, whose own renaissance has carried them back into contention. With elite stuff and an unparalleled strike-throwing ability, Guerrero is a reliable cog.