BOSTON -- Kevin Youkilis will begin a rehab assignment with Triple-A Pawtucket on Wednesday, the next step in his return from a strained lower back.

Youkilis will start as the designated hitter for the PawSox, who begin a four-game series with the Durham Bulls on Tuesday night.

"We're going to try to get him three at-bats tomorrow," said manager Bobby Valentine. "He'll start tomorrow and we'll get him enough [playing time], whatever it's going to take to have him say that he feels good."

The third baseman, who hasn't played since April 28, took batting practice and fielded ground balls for the third straight day on Tuesday before Boston's series finale with Seattle.

Youkilis is likely to play at least two games in the Minors before returning to the Red Sox.

"He looked really good taking his ground balls today, moving around, bounce in his step," Valentine said. "He'll probably go from DH to playing in the field, seeing some pitches."

Youkilis won't be the only player on a rehab assignment for Pawtucket's series with Durham. Starter Daisuke Matsuzaka, who had Tommy John surgery last year, is scheduled to make his fifth rehab start for the PawSox on Thursday.

Youkilis' rehab assignment means rookie Will Middlebrooks will remain in the lineup for now. Middlebrooks started at third base Tuesday for the 12th time since being recalled from Pawtucket on May 2.

Middlebrooks entered Tuesday's game with nine extra-base hits (four homers, five doubles) and 13 RBIs in 11 games, tied with Mo Vaughn for the most by a Red Sox player in his first 11 games since 1918. Vaughn accomplished the feat in 1991.

Doubront OK after getting hit in ear by ball

BOSTON -- Starter Felix Doubront is OK after getting hit on the right ear while playing catch in the outfield Tuesday afternoon at Fenway Park.

"The ball hit off the fungo and I didn't see the ball," Doubront said a short while later in the Red Sox's clubhouse. "[It] just came right to my ear, but I'm fine, I'm good."

Doubront was on the ground in front of the visitors' bullpen in right field before walking off on his own power with trainers by his side.

"Whenever anybody comes off the field, you hold your breath, but he tested fine," manager Bobby Valentine said. "He feels good, he knows where he is, he knows where he's going. Thank goodness it just hit his ear. I think he's going to be just fine."

Doubront's next scheduled start is Thursday vs. the Rays in a 7:10 p.m. ET contest.

"[It] just kind of scared him more than anything," fellow starter Daniel Bard said.

Salty, not Shoppach, behind plate for Beckett

BOSTON -- With the Mariners starting right-hander Blake Beavin on Tuesday, manager Bobby Valentine elected to go with Jarrod Saltalamacchia instead of Kelly Shoppach, who is a weaker hitter against right-handers.

Tuesday's game marked the first time since April 7 that Saltalamacchia served as Josh Beckett's batterymate. In the right-hander's next five starts, Shoppach was behind the plate.

While it appeared Shoppach had taken over for Jason Varitek as Beckett's preferred catcher, Valentine said earlier in the homestand Beckett and Shoppach would not necessarily be paired every time out.

"I'd say it's open," Valentine said. "I don't think [Shoppach catching Beckett has] proved to be the solution to any situations that we're dealing with."

Saltalamacchia's caught Beckett four times overall, and the results haven't been stellar: 19 earned runs in 22 2/3 innings for a 7.54 ERA.

Saltalamacchia felt Valentine just wanted to play the matchups, saying he'll face right-handers while Shoppach will start vs. southpaws.

Worth noting

• The Red Sox sent Double-A Greenville left-hander Hunter Cervenka to the Cubs to complete the April 21 trade for outfielder Marlon Byrd.

• Relief pitcher Andrew Bailey was scheduled for an exam on his injured right thumb with surgeon Thomas Graham in Cleveland on Tuesday. Bailey had surgery on a torn ligament on April 4.

"Everything's gone according to plan," Bailey said over the weekend before leaving town. "I'd say I'd probably start throwing here in the next couple weeks."

• Manager Bobby Valentine praised shortstop Mike Aviles' defense and said he's been pleased with the team's overall defense so far, especially in the infield.

"He's made all the progressions, he's learning to move with hitters and position himself properly and always know the speed of the runner," Valentine said. "He's been huge. The stability of him has been huge for our defense."