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9/1/2013 2:08 P.M. ET

Rookie Medina filling key role in bullpen

HOUSTON -- One of the more pleasant surprises for the Mariners this season has been rookie right-hander Yoervis Medina, who continues to shine in the bullpen and has thrown the most innings of any reliever on the team.

The 25-year-old Venezuelan just converted to the bullpen last year and has flourished since being promoted in mid-April, going 4-3 with a 2.45 ERA in 58 2/3 innings in 54 games. Among American League rookies, he is first in the league in holds (16), third in appearances, third in strikeouts (63) and fifth in strikeouts per nine innings (9.66).

"He's been unbelievable for us, to the point where we are trying to be careful with him because he's so easy to use," manager Eric Wedge said. "He's been so good against right-handers and left-handers. He continues to get better. The way he competes out there with his stuff has been incredible. He's as valuable as anybody we've had down there this year."

Medina's 54 appearances are already the ninth most in club history for a rookie. So while the youngster normally has pitched in Winter Ball in Venezuela, Wedge said that already has been nixed in order to give Medina a needed break.

Wilhelmsen recalled from Triple-A to bolster 'pen

HOUSTON -- Former closer Tom Wilhelmsen was recalled from Triple-A Tacoma on Sunday as the first of several September callups expected to join the Mariners in the next few days.

Wilhelmsen, 29, saved 53 games over the past two seasons for Seattle, including 24 this year, but lost his closing job after blowing his fifth save and was optioned to Tacoma on Aug. 5. He went 0-1 with a 10.50 ERA in eight games with the Rainiers, allowing 19 hits and 14 runs in 12 innings with five walks and 15 strikeouts.

The 6-foot-6 right-hander will be used now as a middle-innings reliever as Danny Farquhar has secured the closing job, converting 11 of 12 save opportunities since taking over that role.

"I'm going to use him in multiple roles, really," manager Eric Wedge said. "I'll just ease him in and see what happens. The sooner we get Tom in there and find out where he is, the sooner we'll get a better idea of how we can use him."

Wilhelmsen said he was ready for anything.

"I might even play shortstop or something," he said with a laugh. "I was starting there, relieving. I was all over the place. Maybe DH. Who knows? We'll see."

Though Wilhelmsen started two games in Tacoma, that was just to control his outing and he never threw more than two innings. The club considered converting him to a starting role a year ago, but that is not in the plans now, Wedge said.

"I still feel with his personality, he's still more of a bullpen guy," Wedge said. "I think he has the pitches to be a starter if he needs to be, but now you're talking about stretching a guy out, taking years to stretch a guy out where he can be a viable starter throwing 170-180 or 200 innings. That's not something that happens overnight without putting him in harm's way."

Wedge acknowledged Wilhelmsen didn't put up great numbers in Tacoma, but said he worked on locating his fastball and getting ahead in counts quicker.

"We've seen him come up here before and do well, even better than he did in the Minor Leagues. So hopefully he can flip that switch again," Wedge said. "I feel strongly that he's going to be a part of this. In what role? I don't know. He has too big an arm and too much experience and too much success in a vital role up here not to be. So I'm hoping all these trials he's gone through will ultimately help him be a better bullpen guy because of what he has gone through. He's seen both sides of it."

What exactly was Wilhelmsen focusing on in Tacoma?

"Throwing strikes. Just trying to throw strikes," said the big right-hander. "It's kind of been that way, not just the last month. That's what you're always trying to do. I guess if my numbers weren't good and I'm working on throwing strikes, that means I'm throwing strikes because they're hitting 'em. So I was successful in doing what I was supposed to be doing."

Wilhelmsen is 0-3 with a 4.37 ERA in 47 games this season for Seattle after going 4-3 with a 2.50 ERA in 73 appearances in 2012.

Zunino to rejoin Mariners on Monday

HOUSTON -- Rookie catcher Mike Zunino will be recalled from his injury rehab assignment and join the Mariners on Monday, in time to catch Felix Hernandez's start in the series opener against the Royals in Kansas City.

Manager Eric Wedge said Zunino will be the second Mariner to join the club as a September callup after reliever Tom Wilhelmsen was added to the roster on Sunday.

"I think there's a good chance you'll see Zunino tomorrow, seeing how he's flying today," Wedge said. "Then we'll wait until after the game on Monday and see some more guys on [Tuesday]."

Tacoma ends its season on Monday. The Mariners didn't want to wait any longer to bring Zunino back, however, as he's now played five rehab games with the Rainiers as he returns from a broken hamate bone in his left hand that has sidelined him since July 26.

Zunino, 22, caught all nine innings of Tacoma's 4-0 win over Sacramento on Saturday, going 0-for-4 at the plate. He's hit .111 (2-for-18) with four runs scored, one triple and three walks.

Zunino was the Mariners' first-round Draft choice last year, the third selection overall. He hit .242 with two homers and 10 RBIs in 29 games for Seattle after being called up on June 11 and immediately taking over as the team's starting catcher.

Worth noting

• When the Mariners beat the Astros, 3-1, on Saturday, it was their first win since Opening Day when they won without having an extra-base hit. Seattle had six singles in its victory over Houston. In the season opener, the Mariners beat Oakland, 2-0, with just five singles.

• Going into Sunday's series finale in Houston, the Mariners bullpen had recorded 11 shutout innings in the first three games of the set and stranded all five inherited runners.

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.