"Right now, that's where we're headed," manager Don Wakamatsu said. "Obviously, the way it slots up down in the Minor Leagues, if we wanted to expedite that 25th guy, we could, but that's the plan going forward."
Wakamatsu said the competition is between Ryan Rowland-Smith, Brandon Morrow and Jason Vargas. Whoever the Mariners go with will have the ball on July 25 against the Indians at Safeco Field.
Each has his strengths, Wakamatsu said.
"[Rowland-Smith] has improved in just about every outing he's thrown down there," Wakamatsu said. "He's stretched out, the quality of the breaking stuff has improved, the velocity is going up."
Wakamatsu added, "You try to find things, whether it be Vargas and his ability to get left-handed batters out, or Brandon to be a little more economical with his pitches and to work on his secondary pitches."
Reading between the lines, Wakamatsu likes different parts of each, and hopes to find a spot for each. And while choosing among the three may be a dilemma, he doesn't see it as much of a problem.
"I feel pretty fortunate we have three down there that we like and who are in our plans for the future," Wakamatsu said. "The rest, you look and you try to define what happened up here and how we can get better for the future.
"We feel pretty strong about having some depth down there."
Although Olson struggled with tempo Thursday against the Indians, Wakamatsu said there were no plans to push him back from Tuesday's start.
"Olson has thrown some good games for us," Wakamatsu said. "... Olson is a guy who can draw on some successes and not focus on the negatives.
"This year, where he's had tremendous success out of the bullpen -- he should just trust the fact that he belongs here. The rest is allowing his stuff to work."
What no one wants, Wakamatsu said, is for Olson to overthink everything, and to worry too much about a bad outing.
"The pressure's amazing at this level," Wakamatsu said. "It's really up to the player, along with the coaching staff, to convince him that he does belong."
Olson's not the only one who will have to carve out his own place. For Morrow, Rowland-Smith and Vargas, stepping back into the Majors will have its own set of challenges.
Rowland-Smith is 4-3 with a 4.56 ERA in nine starts for Triple-A Tacoma, while Vargas has a 1-1 record with a 2.76 ERA in four starts. Morrow, meanwhile, is fresh off his recent demotion to Triple-A on Sunday.
This season, Morrow was 0-4 with a 5.28 ERA. Rowland-Smith, meanwhile, has no record in 3 1/3 innings of work this season in the big leagues. Vargas, meanwhile, is 3-3 with a 3.82 ERA.