BOSTON -- The clock is ticking on Aaron Cook. The right-hander, who has been pitching well for Triple-A Pawtucket, has an opt-out clause in his contract for May 1, which for those without a calendar handy is Tuesday.

As the Red Sox opened a homestand against Oakland, manager Bobby Valentine said no moves had been made related to Cook. However, he did acknowledge a plan to use Cook out of the bullpen.

“If he came here, yes,” Valentine said when asked if Cook would be used as a reliever.

That would seem to strengthen Daniel Bard’s hold on a starting spot. Bard is coming off his best outing as a starter; he allowed two earned runs in seven innings at Chicago on Friday.

Cook is 3-0 with a 1.89 ERA in five starts for the PawSox, including two complete games. He has pitched just once out of the bullpen in the majors since 2003 and was not initially considered a candidate for such a role when he signed with Boston in January.

As Valentine is quick to point out, a baseball season is an evolutionary process. The desire not only to add a veteran arm to the major league staff but to keep Cook in the fold for security purposes has led an alteration to the initial plan.

That doesn’t mean it’s going to be easy.

“It’d be challenging,” Valentine said of using Cook in such a role. “You don’t know what’s going to happen. Right now I couldn’t say that it could be anything other than [pitching in relief].”

Valentine admitted that an upcoming stretch of 20 games in 20 days could alter the plans once again. The manager said using Cook as a sixth starter is “a consideration.”

In other clubhouse news:

* Marlon Byrd will be playing his first game as a member of the Red Sox at Fenway Park. It also marks his first game here since being hit in the face by an Alfredo Aceves offering last May when he was with the Chicago Cubs.

Byrd is 8-for-26 (.308) with an RBI and a walk in seven games with the Sox.

“I’m glad that he’s a Red Sox,” Valentine said. “[Hitting coach] Dave Magadan has worked with him so that I think he’s more comfortable at the plate than when he got here and I think that will continue. He’s had some pretty good at-bats. Played some pretty good center field.”

* Daisuke Matsuzaka is on track to make his third rehab start Friday for Pawtucket. Valentine said the weather could alter that plan. Matsuzaka allowed one run and struck out seven in 4 2/3 innings for Double-A Portland in his prior rehab outing.

* The game marks a reunion of sorts for several players, including Boston outfielder Ryan Sweeney and Oakland outfielder Josh Reddick. They were both part of the Andrew Bailey trade this winter.

Sweeney offered a light moment when a reporter asked him how the markets compare. He laughed out loud and asked back, “Trick question?”

Then Sweeney got a bit more serious in assessing the discrepancy.

“Obviously we’re a little bit of a bigger market, but it’s just baseball,” he said. “Here more you’re probably expected to win a little more. There you want to win but I would say that there isn’t as much pressure.”