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John Brebbia’s bounce back

Last year’s most used reliever looked wrung out to start this season, but have some key changes been made to bring back his utility?

MLB: San Francisco Giants at Minnesota Twins Jesse Johnson-USA TODAY Sports

John Brebbia led the National League in appearances last season with 76, including 11 starts for the San Francisco Giants. He had a tremendous first half — 2.45 ERA, 1.22 WHIP 36 K in 40.1 IP — and you thought, “Hey, the Giants really have a reliable reliever now!”

And then they kept using him. And using him. And using him. A combination of the Giants not having many other great options and perhaps by a bit of draconian design (look no further than what the Rays do to their pitchers to maximize out-getting). In the second half of last season, he had a 4.23 ERA, 1.45 WHIP and 18 K in 27.2 IP; and, it’s actually a bit worse than that. From August 2nd of last season through this past April, he had a 5.29 ERA in 34 IP.

Folks, something’s happened since the start of May, though. John Brebbia... is good again. I know, I know, the life of a reliever is transitory and volatile, and so maybe we shouldn’t believe it. We shouldn’t trust it. Then again, maybe we should — if only for this brief moment in time.

If you’ve been reading me for a while, you know I like to lean on Statcast as a bit of a crutch for material but also because I do see its value in terms of proving or disproving what the eye tells me. My grand thesis has been that Brebbia has looked better this season because the Giants have held off using him every day — and yet, the Giants have used him on back to back days six times already this season, which didn’t happen last season until games 67-68 (Giants won game #50 on the season last night).

So, right away, my eye test is wrong. We’d seen his fastball velocity dip at times already this year and that’s when I thought, “Hey, this guy is struggling,” and then when I saw him hitting 94-96 again I thought, “Hey, this guy has his velocity back — maybe letting him rest more has helped.” Not so! There’s a mechanical issue, a rehab issue, something else has refreshed Brebbia’s skillset here in May.

Again, it may not last because he’s a reliever, but let’s take a look at what’s working.

Hitters are really struggling against him. Based on the quality and quantity of contact, his expected batting average and expected slugging percentage are in the top 8% and 5% of the league, respectively, and his expected weighted on base average of .234 is in the top 3% of the league. His 2.20 xERA (expected ERA) is also in the top 3% of the league. MLB’s glossary defines xERA:

Expected ERA, or xERA, is a simple 1:1 translation of Expected Weighted On-Base Average (xwOBA), converted to the ERA scale. xwOBA takes into account the amount of contact (strikeouts, walks, hit by pitch) and the quality of that contact (exit velocity and launch angle), in an attempt to credit the pitcher or hitter for the moment of contact, not for what might happen to that contact thanks to other factors like ballpark, weather, or defense.


xERA is not necessarily predictive, but if a pitcher has an xERA that is significantly higher than his actual ERA, it should make you want to take a closer look into how he suppressed those runs.

I think a lot of this has to do with the fact that Brebbia’s 34.8% strikeout rate is in the top 5% of baseball. His stuff is above average, but not on the border of above average and great/elite, he’s somewhere between just above average and just about to leave above average. His 94.5 mph average fastballs velocity is in there at #172 on this list of best average FB velocity, and that’s out of 451 ranked with a four-seamer.

[Unrelated: Tyler Rogers is dead last on this list with an average four-seam fastball velocity of 82.7 mph].

Statcast charts that fastball as 68th percentile in velo and 74th in spin. It’s a +1 in run value, so, it’s not a dominant pitch, and yet it’s carrying a 35.7% Whiff Rate and it’s being used as a put away pitch 24.2% of the time.

It’s the slider data that really tells underscores how Statcast defines Run Value. Their definition:

the run impact of an event based on the runners on base, outs, ball and strike count.

It makes a lot of sense that the slider is used to either steal a strike or finish at bat and if Brebbia is using the fastball more to setup the slider, then it makes sense that the one used more might not always have the better run impact. His slider’s 2,606 rpm is the 60th-best spin rate on the slider in baseball. Better than Logan Webb’s (#72 - 2,581) and Shohei Ohtani’s (#74 - 2,578), and by Run Value (-3) it is one of the better sliders in baseball right now, too: #58, tied with Hunter Greene (CIN), Patrick Corbin (WAS), Yusei Kikuchi (TOR), and Shane Bieber (CLE), but also Zack Wheeler and Joe Kelly.

At the beginning of the year, John Brebbia talked about how the Giants approached him after 2022:

They used a lot of data to convince John Brebbia to adjust his approach, it seems, but also something much simpler:

Before he joined the Giants in 2021, Brebbia had thrown the four-seamer more often than the slider (53%). Since joining the Giants, he’s thrown the slider more than the fastball, and this season, he’s throwing the slider even more (54.8%). I think sequencing has also helped, too, but the Giants are making sure Brebbia’s playing to his strengths, and so far, it’s helped turn a shaky season into a dominant month of May: 0.93 ERA, 13 K, 3 BB in 9.2 IP (0.4 fWAR).