← SEA team pageMLB injury reportMLB news
Isaac Mattson
P
SEA
2026 season
- GP
- 38
- W-L
- 0-0
- ERA
- 5.35
- WHIP
- 1.60
- K
- 36
- IP
- 38.2
Game log
| Date | Opp | Result | Dec | IP | H | ER | BB | K |
|---|---|---|---|---|---|---|---|---|
| Sep 5 | vs LAA | L 1-6 | - | 2.0 | 4 | 3 | 0 | 2 |
| Aug 17 | vs DET | L 5-8 | - | 2.0 | 2 | 1 | 2 | 1 |
| Jul 28 | vs AZ | L 7-8 | - | 1.2 | 3 | 1 | 1 | 3 |
| Jul 25 | vs CHC | L 0-11 | - | 0.1 | 4 | 3 | 1 | 1 |
| Jul 19 | @CLE | W 7-1 | - | 1.0 | 0 | 0 | 0 | 1 |
| Jul 18 | @CLE | W 7-1 | - | 1.0 | 1 | 0 | 0 | 2 |
| Jul 12 | vs MIL | W 14-5 | - | 0.2 | 1 | 0 | 1 | 1 |
| Jul 11 | vs MIL | W 3-2 | - | 1.0 | 1 | 0 | 0 | 0 |
| Jul 8 | vs ATL | L 0-3 | - | 1.0 | 2 | 1 | 0 | 1 |
| Jul 5 | @WSH | W 11-5 | - | 1.0 | 2 | 0 | 0 | 1 |
| Jul 3 | @WSH | L 5-9 | - | 1.1 | 3 | 4 | 1 | 1 |
| Jun 30 | @PHI | L 0-8 | - | 0.2 | 1 | 0 | 0 | 0 |
| Jun 27 | vs CIN | L 7-9 | - | 1.0 | 0 | 0 | 0 | 2 |
| Jun 26 | vs CIN | L 4-6 | - | 1.0 | 0 | 0 | 0 | 1 |
| Jun 23 | vs SEA | L 2-3 | - | 1.0 | 0 | 0 | 0 | 1 |
| Jun 17 | @ATH | W 12-4 | - | 1.0 | 1 | 1 | 0 | 2 |
| Jun 14 | vs MIA | L 2-4 | - | 1.1 | 0 | 0 | 2 | 1 |
| May 17 | vs PHI | L 0-6 | - | 1.0 | 1 | 0 | 0 | 0 |
| May 16 | vs PHI | L 0-6 | - | 1.1 | 0 | 0 | 1 | 2 |
| May 10 | @SF | L 6-7 | - | 0.1 | 3 | 2 | 0 | 0 |
| May 7 | @AZ | W 4-2 | - | 0.1 | 0 | 0 | 0 | 1 |
| Apr 30 | vs STL | L 5-10 | - | 0.2 | 3 | 5 | 2 | 0 |
| Apr 27 | vs STL | L 2-4 | - | 0.1 | 0 | 0 | 0 | 1 |
| Apr 25 | @MIL | W 6-3 | - | 1.0 | 0 | 0 | 0 | 0 |
| Apr 24 | @MIL | W 6-0 | - | 1.0 | 0 | 0 | 1 | 1 |
| Apr 19 | vs TB | W 6-3 | - | 1.0 | 0 | 0 | 0 | 1 |
| Apr 18 | vs TB | L 7-8 | - | 1.0 | 0 | 0 | 0 | 0 |
| Apr 16 | vs WSH | L 7-8 | - | 1.0 | 0 | 0 | 1 | 0 |
| Apr 14 | vs WSH | L 4-5 | - | 2.0 | 2 | 0 | 0 | 1 |
| Apr 11 | @CHC | W 4-3 | - | 1.0 | 2 | 0 | 0 | 1 |
| Apr 10 | @CHC | W 2-0 | - | 1.0 | 0 | 0 | 1 | 0 |
| Apr 7 | vs SD | W 7-1 | - | 0.2 | 1 | 0 | 0 | 0 |
| Apr 6 | vs SD | L 0-5 | - | 1.0 | 2 | 0 | 0 | 2 |
| Apr 4 | vs BAL | W 3-2 | - | 1.0 | 1 | 0 | 1 | 1 |
| Apr 1 | @CIN | W 8-3 | - | 1.1 | 1 | 0 | 0 | 0 |
| Mar 30 | @CIN | L 0-2 | - | 1.0 | 0 | 0 | 1 | 1 |
| Mar 29 | @NYM | W 4-3 | - | 1.0 | 0 | 0 | 0 | 2 |
| Mar 26 | @NYM | L 7-11 | - | 0.2 | 3 | 2 | 2 | 1 |
| 2025 season | ||||||||
| Sep 26 | @ATL | W 9-3 | - | 1.0 | 2 | 1 | 0 | 0 |
| Sep 24 | @CIN | W 4-3 | - | 0.2 | 1 | 1 | 1 | 0 |
| Sep 23 | @CIN | W 4-2 | - | 1.0 | 1 | 0 | 0 | 0 |
| Sep 19 | vs ATH | L 3-4 | - | 1.0 | 0 | 0 | 0 | 0 |
| Sep 14 | @WSH | L 3-4 | L | 2.0 | 1 | 0 | 1 | 1 |
| Sep 10 | @BAL | L 1-2 | - | 1.0 | 3 | 1 | 0 | 0 |
| Sep 9 | @BAL | L 2-3 | - | 1.0 | 0 | 0 | 2 | 1 |
| Sep 7 | vs MIL | L 2-10 | - | 1.0 | 0 | 0 | 2 | 1 |
| Sep 3 | vs LAD | W 3-0 | - | 1.0 | 0 | 0 | 0 | 1 |
| Sep 2 | vs LAD | W 9-7 | - | 1.0 | 3 | 2 | 0 | 0 |
| Aug 29 | @BOS | W 4-2 | - | 1.0 | 1 | 0 | 0 | 1 |
| Aug 27 | @STL | W 2-1 | - | 1.0 | 0 | 0 | 0 | 1 |
| Aug 26 | @STL | W 8-3 | - | 1.0 | 0 | 0 | 0 | 1 |
| Aug 24 | vs COL | W 4-0 | - | 1.0 | 0 | 0 | 0 | 1 |
| Aug 20 | vs TOR | W 2-1 | - | 1.0 | 0 | 0 | 0 | 1 |
| Aug 17 | @CHC | L 3-4 | L | 1.0 | 2 | 1 | 1 | 0 |
| Aug 15 | @CHC | W 3-2 | - | 1.2 | 2 | 0 | 1 | 1 |
| Aug 13 | @MIL | L 5-12 | - | 1.0 | 0 | 0 | 0 | 1 |
| Aug 10 | vs CIN | L 8-14 | - | 0.2 | 0 | 0 | 1 | 1 |
| Aug 9 | vs CIN | L 1-2 | - | 1.0 | 0 | 0 | 0 | 2 |
| Aug 6 | vs SF | L 2-4 | - | 0.1 | 2 | 1 | 1 | 0 |
| Aug 3 | @COL | W 9-5 | - | 1.0 | 0 | 0 | 1 | 1 |
| Jul 30 | @SF | W 2-1 | W | 2.0 | 2 | 0 | 0 | 3 |
| Jul 28 | @SF | W 6-5 | - | 1.0 | 0 | 0 | 0 | 2 |
| Jul 25 | vs AZ | L 0-1 | - | 1.0 | 2 | 0 | 0 | 1 |
| Jul 22 | vs DET | W 8-5 | - | 1.0 | 1 | 0 | 0 | 2 |
| Jul 19 | vs CWS | L 4-10 | - | 0.1 | 2 | 2 | 1 | 1 |
| Jul 18 | vs CWS | L 1-10 | - | 1.0 | 0 | 0 | 0 | 0 |
| Jul 9 | @KC | L 3-4 | L | 1.0 | 2 | 1 | 1 | 1 |
| Jul 8 | @KC | L 3-4 | - | 0.0 | 1 | 0 | 0 | 0 |
| Jul 5 | @SEA | L 0-1 | - | 1.1 | 0 | 0 | 0 | 3 |
| Jul 2 | vs STL | W 5-0 | - | 1.0 | 1 | 0 | 1 | 1 |
| Jul 1 | vs STL | W 1-0 | W | 1.0 | 0 | 0 | 2 | 0 |
| Jun 27 | vs NYM | W 9-1 | - | 1.1 | 1 | 0 | 0 | 3 |
| Jun 23 | @MIL | W 5-4 | - | 1.2 | 1 | 0 | 0 | 3 |
| Jun 20 | vs TEX | L 2-6 | - | 1.1 | 1 | 0 | 1 | 1 |
| Jun 19 | @DET | W 8-4 | - | 0.2 | 2 | 2 | 0 | 0 |
| Jun 15 | @CHC | L 2-3 | - | 2.0 | 0 | 0 | 0 | 0 |
| Jun 12 | @CHC | L 2-3 | - | 1.2 | 0 | 0 | 1 | 1 |
| Jun 10 | vs MIA | L 2-3 | - | 2.0 | 0 | 0 | 0 | 3 |
| Jun 7 | vs PHI | W 2-1 | W | 1.0 | 0 | 0 | 0 | 1 |
| May 25 | vs MIL | L 5-6 | - | 1.1 | 0 | 0 | 1 | 1 |
| May 23 | vs MIL | W 6-5 | - | 0.2 | 0 | 0 | 0 | 1 |
| May 22 | vs MIL | L 5-8 | - | 1.0 | 1 | 1 | 0 | 2 |
| 2024 season | ||||||||
| Sep 29 | @NYY | L 4-6 | - | 2.0 | 0 | 0 | 1 | 3 |
| Sep 24 | vs MIL | L 2-7 | - | 1.1 | 1 | 3 | 4 | 1 |
| Sep 20 | @CIN | L 3-8 | - | 2.0 | 0 | 0 | 0 | 2 |
Latest news
The Mariners claimed Mattson off waivers from the Pirates on Monday, Colin Beazley of the Pittsburgh Post-Gazette reports.
Mattson posted a 2.45 ERA and 45:19 K:BB over 47.2 innings in 2025, but he stumbled in 2026 with a 5.35 ERA and 36:18 K:BB over 38.2 frames. The 31-year-old will look to fill a middle-relief role in Seattle.
RotoWire via ESPN · 4d ago
The Pirates placed Mattson on the 15-day injured list Tuesday, retroactive to Sunday, with hip inflammation.
Mattson gave up three earned runs in two innings during his first appearance back in the majors Saturday and appears to have picked up an injury in the process. He'll be eligible to return during the final week of the regular season. In the meantime, the Pirates will bring up Brandon Eisert to fill the void in their bullpen.
RotoWire via ESPN · Sep 8
The Pirates recalled Mattson from Triple-A Indianapolis on Friday, Danny Demilio of PittsburghBaseballNow.com reports.
The right-hander has been shuttled between Triple-A and the majors throughout the season. Mattson has pitched in 37 MLB games in 2026 and has a 4.91 ERA, 1.58 WHIP and 34:18 K:BB over 36.2 innings.
RotoWire via ESPN · Sep 4
The Pirates optioned Mattson to Triple-A Indianapolis on Tuesday, Jason Mackey of MLB.com reports.
Mattson was needed for two innings and 41 pitches in Monday's loss to the Tigers, so he wasn't going to be available for a day or two. Antwone Kelly will absorb Mattson's spot on the roster and in the bullpen.
RotoWire via ESPN · Aug 18
The Pirates recalled Mattson from Triple-A Indianapolis on Thursday.
Mattson was sent down earlier this month after posting a 4.93 ERA, 1.56 WHIP and 33:16 K:BB over 34.2 innings. He'll aim for more consistency with the Pirates this time around.
RotoWire via ESPN · Aug 13
The Pirates optioned Mattson to Triple-A Indianapolis on Sunday.
The right-hander was just called up Saturday and will return to Indianapolis without making an appearance. Mattson has been inconsistent across 36 big-league outings this year with a 4.93 ERA, 1.56 WHIP and 33:16 K:BB over 34.2 innings.
RotoWire via ESPN · Aug 2