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04/28/12 10:36 PM ET

Cook now an option to pitch out of bullpen

CHICAGO -- Veteran right-hander Aaron Cook, with 72 Major League wins under his belt, made his fourth and likely final Minor League rehab start Saturday for Triple-A Pawtucket.

Cook, who allowed three runs on five hits and struck out five over 6 1/3 innings for a no-decision in Pawtucket's 6-4 loss, has an opt-out clause in his contract that he can exercise by May 1. Once the Red Sox hear what his decision is, they have 48 hours to decide whether to activate him. Cook has another opt-out clause on June 1.

While there doesn't seem to be an opening in Boston's starting rotation, an alternative scenario could emerge -- one in which Cook could work as a reliever.

Back in Spring Training, manager Bobby Valentine unequivocally stated that relief was out of the question for Cook because of his history of shoulder woes.

But it appears things have changed.

"There have been discussions, yep," said Valentine. "[Pitching coach] Bob McClure thinks that after talking with him, that it's feasible. Initially there was no [thought of it]. I think I told you guys initially in Spring Training that [relief] was a non-factor. It was a non-consideration. Reports are that he's never felt better about his shoulder, or he hasn't felt this good about his shoulder in a long time."

Cook, with a solid sinker and a wealth of experience, could provide some stability for a Boston bullpen that has struggled this season.

"What surprised me was, with Aaron's shoulder, the trainers did such a good job with him this spring that, when I talked to him right before we broke [camp], he said he felt like he could pitch out of the bullpen," McClure said. "Before, I don't think he could have physically -- got up, got down, up. He said his shoulder hadn't felt this way in three or four years.

"That being said, right before we broke camp, I asked him, and he said he could. That still remains to be seen, but if a guy tells you that, you've got to think maybe he could."

Byrd finding his groove with Red Sox

CHICAGO -- Marlon Byrd was in an epic slump with the Chicago Cubs? You'd never know it by watching his first few days with the Red Sox.

Byrd is hitting .333 for the Red Sox and has at least one hit in his first six games with the team. This, after he went just 3-for-43 with the Cubs.

He cites a couple of different reasons for his turnaround, including some work in the batting cage with new hitting coach Dave Magadan.

"He looked at my 2009 at-bats and 2010 at-bats and tried to just simplify things, getting me to my old stance, getting my hands back as far as I can early and then seeing the ball and hitting it," Byrd said. "I'm still working."

And according to Byrd, being part of a prolific offense has played no small role in how he is hitting the ball.

"Hitting is contagious," Byrd said. "You see these guys hitting, for some reason, it always clicks like that.

"It's just a combination of things, change of scenery, being comfortable, knowing that at some point the ball was going to fall. Having guys in front of you in the lineup, seeing how they pitch, seeing the guys hitting. It's a combination of things. The good thing is I'm finally hitting, thank goodness."

The Red Sox are 6-0 with Byrd in the fold. This, after a 4-10 start.

"I just like his energy. He's got bounce in his step," said manager Bobby Valentine. "He's ready to go. I don't want to say it's contagious or it's anything we needed, but it was a great, added feature to our group. And his at-bats, we're getting used to his approach and his at-bats, but he's getting hits. That's all that matters."

Dice-K dazzles in second rehab outing

CHICAGO -- Right-hander Daisuke Matsuzaka had an encouraging second start of his Minor League rehab assignment, giving up one run and striking out seven in 4 2/3 innings for Double-A Portland on Saturday.

Matsuzaka walked two and allowed three hits, throwing 74 pitches, 44 of which were for strikes.

The Red Sox expect Matsuzaka will make three more starts in the Minors before re-joining the Red Sox. He underwent Tommy John surgery last June.

His next start will likely be either at home for Double-A Portland or in Toledo for Triple-A Pawtucket.

Ian Browne is a reporter for MLB.com. Read his blog, Brownie Points, and follow him on Twitter @IanMBrowne. This story was not subject to the approval of Major League Baseball or its clubs.