Gearrin will serve as the opener for Monday's game against the Astros, Greg Johns of MLB.com reports.
Gearrin will likely pitch one or two innings before giving way to left-hander Wade LeBlanc, who is expected to cover the majority of innings Monday. In 26 appearances this season (all in relief), Gearrin owns a 3.22 ERA, 1.34 WHIP and 27:13 K:BB in 22.1 innings.