Brayan Bello Is Going Through It

Things could be going better for Brayan Bello. I guess that’s true of most Red Sox players these days, but the right-hander is having an especially rough go of things. On Sunday, Bello took the decision in an 8-1 loss to the Braves, allowing seven earned runs in five innings pitched.

That kind of line doesn’t necessarily signal a terrible outing; sometimes a starter trudges along in quality-start territory before running into trouble late. A couple quick walks, then the bullpen lets a couple inherited runners score… three runs allowed over four innings can turn into seven runs in five innings in a flash.

That wasn’t the case here. Seven of the first 10 Braves hitters reached base; five of them scored. Manager Chad Tracy let Bello wear it until he’d reached five innings and 98 pitches. And it was Bello’s 27th birthday on Sunday, too. Usually you only hear “wear it” on a guy’s birthday in the context of a party hat or a new shirt.

That’s how Bello’s season has gone. It looks ugly (2-5, 7.16 ERA, with 30 strikeouts, 20 walks, and 10 home runs in 44 innings). And when you scratch the surface (6.56 xERA, 6.05 FIP) it’s just as bad as it looks.

Bello has never been Boston’s ace, but since 2023 he’s made 93 starts and thrown 530 innings, both tops among Red Sox pitchers by more than 50%. He’s made at least 28 starts and thrown at least 150 innings in each of the past three full seasons, and he’s done it with an ERA- of 93 from 2023 to 2025. That’s not an ace, but it’s the kind of steady mid-rotation starter you need to get through a long regular season without killing your bullpen.

From 2023 to 2025, the Red Sox had a .605 winning percentage in games Bello started. This year, they’re 1-6, not counting two bulk relief stints. Boston’s awful start isn’t entirely or even mostly Bello’s fault — if they’d won every game Bello appeared in, the Red Sox would still be more than a series out of first place — but this is a pretty big piece of the foundation that’s gone all wobbly.

Ordinarily I’m reticent to deliver definitive conclusions about a pitcher’s welfare based on seven weeks’ worth of games, but there’s a smoking gun here: Bello changed his arm angle. For his whole career up to this point, he has lived in the low 30-degree range; last year, it was 33 degrees. This year, his arm angle is up to 42 degrees.

I think it’s easy to overstate the importance of arm slot over time; Devin Williams has a different release point for his fastball and changeup, and that doesn’t seem to hurt him much. So whether the arm angle change is the cause of Bello’s woes or a symptom of some larger systemic issue, the real problem is he’s lost about a mile an hour of velocity this year, and his fastballs — all three of them — are getting crushed.

His most common pitch is his sinker, which he tunnels with his changeup to left-handed hitters. Those two pitches have an overlapping induced movement profile, so from the hitter’s perspective, the difference between the two is as follows: The changeup comes in a couple miles an hour slower than the sinker, and by virtue of being in the air longer, it drops more.

Bello uses this to his advantage — when he’s pitching well, he can throw sinkers for strikes and then paint the lower outside edge of the zone with changeups. This year, the velocity difference between the two pitches has shrunk, which makes them blend.

But he is also leaving more hittable changeups over the heart of the plate. Last year, only 9.5% of his changeups ended up in Statcast’s Heart zone. This year, that’s up to 22.7%. And it gets worse when you look at his four-seamer.

Truth be told, Bello’s four-seamer has never been great; it’s got average velocity and dead-zone movement. There’s a reason he throws mostly sinkers. But his four-seamer is still useful as a chase pitch and to keep hitters from sitting on the sinker. Usually, Bello throws the fastball up in the zone, or even above it.

This year, he started out by significantly de-emphasizing his four-seamer. He threw it 15% of the time across 2025, but just 3.8% of the time in April. At the same time, his cutter usage jumped from 16% to 23%.

Bello has calmed down in May and is now throwing four-seamer and cutter in more or less equal proportion. And the results have been better than they were in the first month of the season. I made a big stink about his bad outing on Sunday, but Bello pitched well in two bulk relief appearances earlier in May. Coming in after Jovani Morán against the Tigers, and a week later against the Phillies, Bello struck out seven in seven innings against Detroit and five in 6 1/3 innings against Philadelphia. In both cases, he allowed one walk, four hits, and a single earned run. Those two outings dropped his FIP exactly two runs from where it was at the end of April.

So yeah, on one hand he’s better when he throws the four-seamer more and the cutter less. On the other hand, opponents are hitting — and this is not a typo — .778 against Bello’s four-seamer this season. Generally, hitters run better stats against the four-seamer than against other pitches, but not batting averages that would pass as a good free throw shooting percentage.

What’s happening here is that where Bello used to throw his four-seamer at the top of the zone, now he’s missing high constantly. Last year, he threw 53.4% of his fastballs in the zone. Here’s the heat map:

Almost always up, but more often than not in the zone. The four-seamer was the pitch opponents hit best last year, but a .343 wOBA and .291 xwOBA isn’t bad for a four-seamer.

This year, Bello’s either totally lost his fastball command or he’s throwing high on purpose. Only 31.8% of his four-seamers have been in the strike zone this year, and if that’s a deliberate strategy, it is super not working.

He’s only gotten a hitter to chase him up the ladder five times so far this year, with zero swings and misses and two hits off three balls in play. In the zone it’s even worse: On 14 four-seamers in the zone, Bello has gotten 11 swings, two whiffs, three foul balls, and six balls in play. Five of those turned into hits, and all of them had exit velos of at least 102 miles per hour. The sixth was a sacrifice bunt.

In other words, Bello’s four-seamer has led to seven hits and three outs this season, and one of those outs was on purpose. This is the pitch whose reintroduction has arguably made him more effective, because the cutter wasn’t working either. He does get a decent amount of in-zone whiffs with his cutter, but when he’s not locating the pitch well, he’s getting torched.

You see the problem. He’s already given up as many home runs on cutters in 2026 as he did in all of 2025.

There are lots of ways to get hitters out consistently, but generally a pitcher needs at least one of velocity and command, and Bello has been bleeding both this year. Big league hitters are good; throw them 88 middle-middle and you’re only going to get one outcome. I don’t know what the answer is, but Bello had better find it soon.