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.