SEATTLE -- It could be jumping the gun just a little, but if there's an opening in the Mariners' starting rotation, recently promoted left-hander Jason Vargas just might move into that spot.

After not pitching at all last season because of hip surgery, Vargas made his Mariners debut on Sunday afternoon, pitching the final 2 1/3 innings in Seattle's 15-inning victory over the Athletics.

"I was really impressed with the fact that he wasn't afraid of anything," manager Don Wakamatsu said on Monday. "He pitched aggressively, challenged hitters and threw strikes. You'd like to be able to ease him into it, but we threw him into the fire."

The heat has been turned up on right-hander Carlos Silva, who has been told to improve or lose his spot in the rotation. Silva, who is 1-2 with a 7.36 ERA this season after losing 15 of his final 16 decisions last season, is scheduled to start against the Royals on Wednesday.

Asked during his pregame media session on Monday if he would hesitate to put Vargas in the rotation, Wakamatsu never hesitated.

"Not after what I saw yesterday," he said.

Vargas surrendered two hits, walked one and struck out four batters in his debut game.

Acquired from the Mets in the J.J. Putz deal last December, Vargas has been a starter most of his career and was in the Tacoma Rainiers rotation this season.

"I've always been a starter, but the first time I got called up [with the Mets], I pitched out of the bullpen," he said. "It's not that unfamiliar to where it's uncomfortable. I kind of look at it like it's an opportunity to get into more games.

"Being a starter is definitely more comfortable because that's what I've done more, but having a chance to go out there a couple times a week is definitely something to look forward to. You have a lot of chances to get out there and get into the action."