The Pirates are shuffling their bullpen again, and this time the move comes with a trip to the injured list for Isaac Mattson.
Pittsburgh placed the right-hander on the 15-day IL with right hip impingement before the series opener against the Chicago White Sox at Rate Field on Sept. 8, retroactive to Sept. 6. To fill the spot, the Pirates recalled left-handed reliever Brandon Eisert from Triple-A Indianapolis.
It’s the second bullpen injury the Pirates have dealt with in the past week. Kirby Yates is already on the 15-day injured list with right shoulder impingement.
Mattson’s season has gone in two very different directions. He was one of Pittsburgh’s most effective bullpen arms in 2025, but he hasn’t come close to matching that level this year. In 38 games and 38.2 innings pitched, he owns a 5.35 ERA with 36 strikeouts, 18 walks, a .282 batting average allowed and a 1.60 WHIP.
The Pirates have moved him back and forth between Pittsburgh and Indianapolis five times, including three times since Aug. 1.
He opened 2026 well, putting up a 1.13 ERA through his first 13 appearances. But everything changed after he allowed five runs against the St.
Louis Cardinals at PNC Park on April 30, a 10-5 loss. Since then, he has posted an 8.34 ERA over his last 22 outings.
The underlying numbers haven’t helped his case either. Opponents have done damage with a 52.1% hard-hit rate and a 12.4% barrel rate against him, marks that would place him near the bottom of the league if he were qualified.
His most recent appearance, against the Los Angeles Angels at PNC Park on Sept. 5, also went sideways. Mattson gave up three runs in his second inning of work during the Pirates’ 6-1 loss.
He’s eligible to come off the injured list on Sept. 21, which leaves open the possibility of a return for the final two series of the season.
Pittsburgh is carrying 10 pitchers in the bullpen right now, a number shaped by Mitch Keller’s season-ending injury and the expanded September rosters. The group includes seven right-handers - Lake Bachar, Khristian Curtis, Wilber Dotel, Camilo Doval, Carmen Mlodzinski, Yohan Ramírez and Luke Weaver - along with lefties Eisert, Mason Montgomery and Gregory Soto.
Bachar is expected to handle the start of the bullpen game in the next matchup with the White Sox on Sept. 9.
Curtis, Dotel, Mlodzinski and Ramírez are lined up as middle-relief options, while Doval and Weaver, along with Eisert and Soto, can cover an inning if needed. Montgomery has been excellent in the closer role.
The Pirates will need that group to carry a heavy load as they try to make a late push toward the postseason.
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