NEW YORK -- Mariners left-hander Erik Bedard will return to the rotation on Friday against Tampa Bay at Safeco Field after missing four starts with a sprained left knee, manager Eric Wedge said Monday.

Bedard went 4-6 with a 3.00 ERA in 15 starts before injuring his knee during a 3-1 loss to the Braves on June 27.

Rookie Blake Beavan started the last four games in Bedard's place, and went 1-2 with a 3.04 ERA. Beavan remains on the roster for now, and Wedge didn't indicate what roster adjustment would be made when Bedard returns, but the logical move would be to return Beavan to Triple-A Tacoma when Bedard is activated.

Bedard threw 40 pitches in a two-inning simulated outing on Saturday. Wedge said the veteran would be on a pitch count in his first game back, but declined to say what that limit would be.

"We'll pull him back a little bit, but he should be fine," Wedge said.

Struggling Smoak says thumb is fine

NEW YORK -- While Justin Smoak has been struggling badly at the plate for the last month, the Mariners' young first baseman said that has nothing to do with a right thumb that he's had taped up recently.

Smoak has hit just .138 (9-for-65) since July 2 as his batting average has dipped to .224. He hasn't hit a home run since June 12 in Detroit, remaining stuck on 12 for six weeks now.

Manager Eric Wedge said Smoak has a "little zinger" between his thumb and forefinger, but nothing serious. And Smoak insists his difficulties aren't related to any hand problems.

"I've just got a little blister, so I've got a pad on it to try not to bust it open," he said. "I've got another one on this other side. It's a little sore. I've been swinging a lot. There's been a lot cage work going on here. I'm just trying to get it right."

Smoak, 24, is critical to the Mariners' offensive plans, and Wedge continues penciling him into the lineup, though he was dropped to seventh in Monday's order for the opening game of the Yankees series.

"I'm just trying to slow things down and not rush and swing at bad pitches," Smoak said. "It's one of those things where you just have to keep doing whatever it takes."

The switch-hitting Smoak took that approach Sunday in Boston, when he batted right-handed against right-hander Tim Wakefield, trying a different tactic against the veteran knuckleballer. He doubled in his first at-bat and finished 1-for-3 against Wakefield.

"It was a lot better than left-handed, which I did when I faced him last time," Smoak said. "Wedge talked to me about it beforehand because he had Victor Martinez do that in Cleveland. Against a left-hander, [Wakefield has] more room to throw at and let the ball jump and do different stuff, where as a right-hander, he's got to get it in there without trying to hit you."

Like all the Mariners, Smoak is battling hard to turn things around. The club's 15-game losing streak -- entering play Monday -- was wearing on everyone, including the youngster from Goose Creek, S.C.

"It's tough. We're trying to win every game," he said. "To lose this many in a row, you've got to grind it out. Today is a new day and you've got to do whatever it takes to win that next ballgame."

Kelley set to begin rehab work in Tacoma

NEW YORK -- Right-handed relief pitcher Shawn Kelley will fly to Tacoma on Tuesday and pitch Wednesday for the Triple-A Rainiers as he begins a Minor League rehab stint to test his recovering throwing elbow.

Kelley underwent a procedure on his right elbow last Sept. 1, what the Mariners called "partial Tommy John surgery," and has been working this season toward a comeback. He threw three games for Double-A West Tenn this spring before having to shut things down again, but now is ready for another shot.

He threw two innings of a simulated game Saturday in Boston, and now will take the next step.

"It's very exciting," Kelley said Monday in the Mariners' clubhouse at Yankee Stadium. "Like I've said before, I'll be ultimately excited when I'm back here, but this is the last step. I'll be seeing hitters and pitching in games with a scoreboard and people in the stands. It's a little more realistic and, hopefully, it goes well, which I'm pretty sure it will, because I'm feeling really good."

Kelley remains cautious because of his recent history, but is eager to get back to the point which allowed him to pitch in 67 games for Seattle in 2009-10, with a 4.31 ERA.

"This will be the third time in the last year I've gone on a rehab assignment," he said. "I've had surgeries and setbacks, but I feel better now. Hopefully, we've worked out all the kinks."

Worth noting

• Mariners infielder Chone Figgins was not with the team pregame Monday, and manager Eric Wedge said he wasn't sure on the veteran's availability as he continues dealing with a "personal family emergency."

• Dustin Ackley's .505 slugging percentage through Sunday's game is the third-highest for a rookie second baseman (with a minimum of 100 at-bats) since 1950. The only higher numbers belonged to Bobby Hofman of the New York Giants (.544 in 169 at-bats in 1953) and Bret Barberie of Montreal (.515 in 136 at-bats in 1991).

Bret Boone holds the highest slugging percentage by a Seattle rookie second baseman at .443, over 271 at-bats in 1993.

• Ackley is looking to become just the fifth Mariners rookie to average a hit per game (with a minimum of five games). He currently has 33 hits in 30 games. Previous rookies to pull off that feat were Alvin Davis, Danny Tartabull, Ichiro Suzuki and Kenji Johjima.

• After blowing an early 2-0 lead Sunday in Boston, the Mariners have now lost seven straight games in which they scored first. Prior to that stretch, starting July 7 at Anaheim, they had been 26-10 when scoring first.

• The Mariners announced the signing of University of Oregon catcher Jack Marder, a 16th-round pick in the 2011 First-Year Player Draft. Marder made his Minor League debut Sunday with High Desert in the Class A Advanced California League, and went 2-for-3 with a double. Seattle has now signed 35 of its 51 selections, though the top four -- including first-rounder Danny Hultzen -- remain unsigned.