Pruitt will serve as the Athletics' opening pitcher in Wednesday's game against the Mariners, Ryan Divish of The Seattle Times reports.
Ken Waldichuk (calf) had been the listed starter for Oakland, but he's now instead expected to work in bulk relief. Pruitt carries a 3.38 ERA, 1.50 WHIP and 7:5 K:BB in 10.2 innings this season out of the Oakland bullpen.