Pryor's addition provides extra support in a bullpen that already was carrying an extra arm, while Walker will now be able to start twice in Tacoma, beginning Saturday against Fresno, to stay sharp over next week's All-Star break and then rejoin the club to face the Mets on July 22.
McClendon had already said that Felix Hernandez has been pushed back a day to start Friday's series opener against the A's. Walker had tentatively been projected to start Saturday, but his departure sets up Hisashi Iwakuma to start that day on normal rest and Chris Young to do the same on Sunday.
The risky part of that equation would be going with all relievers in Thursday's series finale with the Twins, but Wilhelmsen has been outstanding in longer relief stints of late and has twice pitched three innings. McClendon said he's tinkered with the notion of Wilhelmsen working into a starting role.
"He's been impressive in the long role," McClendon said. "It's certainly intriguing, something that's been on my mind. We'll see. He's a power arm, he's got three to four quality pitches and he's thrived in that long role. He seems to cherish it a little bit. It's kind of interesting."
McClendon said he's looking at three or four innings maximum out of Wilhelmsen in Thursday's spot start and the big right-hander said he's happy to give it a shot.
"We had talked about it a few days ago," said Wilhelmsen, who was Seattle's closer parts of the past two years and has put up a 2.49 ERA in 47 innings in 33 appearances this year. "We knew it was going to be a bullpen start and I said I was up for it if he needed me to fill in. I'm excited to get the opportunity and say I started a Major League game."
The Mariners sent Wilhelmsen to Double-A Jackson to get some starts midway through his rookie season in 2011, but ended that experiment after he went 4-5 with a 5.49 ERA. But he said he's started plenty of games while growing up and understands the routine.
"I think most of the guys in the bullpen were starters at some point," he said. "It's not like I'm playing football. Maybe it's a little different mindset, but I'm not going to try to look at it that way."
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.