The Pittsburgh Pirates recently acquired two players from the Chicago White Sox for their Competitive Balance Round A pick (along with relief prospect Jaden Woods). The player most fans are focusing on is infield prospect Jacob Gonzalez. After all, he was one of the Sox’s top prospects and was their first-round pick in 2023. However, don’t sleep on the other player the Bucs got in the trade, Brandon Eisert.
On the surface, Eisert’s 5.98 ERA and 4.50 FIP are nothing to be too proud of. However, there is substantial evidence suggesting this is more or less a fluke. The lefty has a 27.4% strikeout rate and a 6.8% walk rate over 27.1 innings pitched. He is one of just 17 lefty pitchers this year with a K-BB% over 20% in at least 20 IP. He surpasses the likes of Aroldis Chapman, Reid Detmers, Ranger Suarez, and Parker Messick. K-BB% has a higher correlation to future ERA than many stats that are built to predict future ERA.
Speaking of stats built to predict future performance, they all suggest Eisert is getting unlucky. He has a sub-3.50 xERA (3.43), xFIP (3.38), and SIERA (3.14). Once again, Eisert ranks highly in many of these numbers. He has the 20th best xFIP, and 15th best SIERA among lefty pitchers with 20+ IP. He also has the 38th lowest xERA.
Eisert’s four-seam fastball is one of the most unlucky pitches in the game. Opponents have nearly a .400 wOBA against it, at .397. However, his xwOBA comes in at just .254, and he induces a whiff rate of 28.4% with the offering. Only 26 pitchers have thrown at least 150 four-seam fastballs with an xwOBA below .260. Of those 26, only 15 have a whiff rate over 25% with their four-seamers. Eisert’s four-seamer has induced a lower xwOBA than fastballs from the likes of Shohei Ohtani, Mason Miller, and Logan Webb, and a higher whiff% than now-Pirates teammate Jared Jones, Nolan McLean, and Chris Sale have induced with their fastballs. The 143-point difference between his wOBA and xwBOA is the 2nd highest as well.
His fastball isn’t the only pitch that has induced good underlying numbers. Eisert’s slider has a 34.5% whiff percentage and a .307 xwOBA. The lefty’s change-up also has a sub-.300 xwOBA at .280, and a whiff percentage over 30% at 32.7%. Eisert has also yet to give up a hit this year with his sinker, and has held opponents to just an 81.2 MPH exit velocity with the pitch.
Eisert is a soft-tosser, who sits 90 MPH with his fastball. However, don’t be completely fooled by his velocity. Eisert’s extension off the mound comes in at 7.2 feet. That makes his velocity play up by nearly 1.5 MPH. His four-seamer out of the hand gets to the plate like a fastball coming in around 91.5 MPH instead of 90 MPH. That also means that his other pitches look faster out of the hand than the radar gun says.
Eisert’s struggles primarily stem from his inability to keep the ball in the yard. He has a 1.98 HR/9 ratio this season. However, his 7.8% barrel rate and 89.2 MPH exit velocity are both about league average. Opponents have a 19.4% HR:FB ratio against Eisert. That is unsustainable if he keeps up a similar exit velo and barrel%. For reference, three qualified hitters this year have a HR:FB ratio between 19% and 20%. That includes Matt Olson, Max Muncy, and Mike Trout. Between them, the lowest average exit velocity is Max Muncy’s 90.4 MPH mark, and the lowest barrel rate comes from Muncy as well, at 13.8%.
The surface numbers for Eisert aren’t very good. However, there is plenty to suggest that there is much more in the tank for Eisert. He gets plenty of swings and misses, does not walk very many, and usually does not get hit very hard. That is typically a good foundation for finding success for a pitcher.
