Full Breakdown
Pirates Adjust Bullpen: Isaac Mattson to IL, Brandon Eisert Recalled
9/9/2026, 11:38:14 AM
Core Event – Mattson to Injured List, Eisert Returns
The Pittsburgh Pirates placed right-handed reliever Isaac Mattson on the 15-day injured list because of a right-hip impingement and, on the same day, recalled left-handed pitcher Brandon Eisert from Triple-A Indianapolis to fill the roster spot. The IL placement was made retroactive to September 6.
Background & Context
Mattson, a 31-year-old product of the University of Pittsburgh, entered the 2024 season with the Pirates after being acquired from the Chicago White Sox on July 11 in a trade that also sent infielder Jacob Gonzalez to Pittsburgh. Prior to the move, Mattson had logged a 5.35 ERA over 38 2/3 innings in 38 relief appearances for the Pirates this season.
The bullpen had already been thinned by the placement of right-hander Kirby Yates on the 15-day IL with a right-shoulder impingement a week earlier. The Pirates therefore turned to Eisert, a left-hander who began the season with the White Sox and was part of the July 11 trade.
Timeline
- July 11 – Pirates acquire Brandon Eisert and infielder Jacob Gonzalez from the White Sox in exchange for left-hander Jaden Woods and future considerations.
- April 30 – Mattson’s performance declines sharply, posting an 8.34 ERA over his last 22 outings after a poor start to the season.
- September 6 – Mattson is placed on the 15-day IL (retroactive) for a right-hip impingement; Eisert is recalled from Triple-A Indianapolis.
Data & Statistics
- Isaac Mattson: 5.35 ERA, 36 strikeouts to 18 walks, 1.60 WHIP in 38 2/3 innings across 38 games (team records).
- Brandon Eisert: 6.23 ERA and 1.85 WHIP with nine strikeouts and four walks in 8 2/3 innings over nine appearances for Pittsburgh this season; overall 2-2 record with a 6.00 ERA in 36 innings across 34 games (combined Pittsburgh and Chicago statistics).
- Bullpen composition: The Pirates carry ten pitchers in the bullpen, including seven right-handers (Lake Bachar, Khristian Curtis, Wilber Dotel, Camilo Doval, Carmen Mlodzinski, Yohan Ramírez, Luke Weaver) and three left-handers (Eisert, Mason Montgomery, Gregory Soto).
Official Statements & Responses
The organization’s roster move was described as a “bullpen adjustment” ahead of the upcoming series against the Chicago White Sox.
Impact on Bullpen & Postseason Push
With the addition of Eisert, the Pirates retain flexibility to match left-handed hitters and preserve innings across the bullpen. The team’s expanded September roster provides an extra arm, allowing the bullpen to absorb the loss of Mattson and Yates while still offering middle-relief options such as Curtis, Dotel, Mlodzinski, and Ramírez. The Pirates are seeking a strong bullpen performance to support a late-season run for a postseason berth.
Conflicting Reports & Gaps
All sources report consistent ERA figures for both Mattson (5.35) and Eisert (6.23). No substantive discrepancies were identified regarding the nature of Mattson’s injury or the terms of the July 11 trade. However, detailed medical information about the severity of Mattson’s hip impingement and the expected timeline for his return beyond the standard 15-day IL period remain unspecified.
