The Mariners purchased Povse's contract from Double-A Arkansas on Sunday, Shannon Drayer of 710 ESPN Seattle reports.
In order to clear a spot on the 40-man roster for Povse, the Mariners designated Dillon Overton for assignment and optioned Rob Whalen to Triple-A Tacoma. Povse has worked exclusively as a starter with Arkansas, registering a 3.46 ERA and 32 strikeouts in 39 innings, but it's expected that he'll work in long relief while he remains with the big club.