Of American League relief pitchers who have made no starts this season, Wilhelmsen ranks second in the league with his 12 innings, just behind Yankees right-hander David Phelps, who has pitched 12 1/3 innings.
The 28-year-old has given the Mariners the quality arm they had hoped for in the back of the bullpen. He's been touched up only twice, for a total of three earned runs, this season.
Manager Eric Wedge talked about Wilhelmsen's growth after Tuesday's 7-4 win against the Tigers. Wilhelmsen allowed the first two runners to reach in a two-run game, before settling down and ending the threat on a flyout and two strikeouts.
"He's very mature," Wedge said. "He's been out in the real world and then back into baseball. He's a good worker. He has a lot of fire in his belly. He's suited to be pitching late in ball games, and he's done a nice job for us."