OAKLAND -- Left fielder Carl Crawford opened the Double-A portion of his Minor League rehab assignment on Tuesday night, going 1-for-2 with two walks for Double-A Portland.

Crawford stole a base and scored a run. And befitting the type of season it's been for him, there was also a health scare. In his second at-bat, Crawford fouled a ball off his right knee.

"It's one of those things where you'll know tomorrow how it feels. Right now, it's not as bad as it looked. It's not too bad right now," Crawford told reporters after the game. "I just hoped I hadn't broken it. I hit it so hard, at the time I was just hoping everything was OK."

Jacoby Ellsbury will join Crawford with Portland on Wednesday for the start of a road series against the New Hampshire Fisher Cats.

The Red Sox haven't said yet when the two outfielders will be activated, but the start of the second half at Tropicana Field against the Rays could be a reasonable estimate.

"I'm pretty sure they have a target, but I don't know what it is just yet," Crawford said. "Hopefully it will be sooner than later."

Neck injury lands Dice-K on disabled list

OAKLAND -- Right-hander Daisuke Matsuzaka was placed on the 15-day disabled list on Tuesday, one day after he was shelled during an abbreviated outing against the Athletics in which he gave up gave up four hits on five runs and threw a career-low of 28 pitches in the Red Sox's 6-1 loss.

Clearly, Matsuzaka was hampered by a neck injury which prevented him from making a side session between starts. It is the same injury -- to the trap muscle on the right side -- that caused him discomfort during Spring Training and in late May, when he was on his Minor League rehab assignment.

Matsuzaka has made just five starts since coming back from Tommy John ligament transfer surgery, going 0-3 with a 6.65 ERA.

"Daisuke, that neck thing, we're going to try to give it some more time and see if it goes away for good this time," said manager Bobby Valentine.

To replace Matsuzaka on the roster, the Red Sox recalled corner infielder Mauro Gomez from Triple-A Pawtucket. Gomez, who had one short stint with Boston earlier this season, is having a monster year at Triple-A Pawtucket, hitting .311 with 19 homers, 55 RBIs and a .980 OPS.

"Mauro has been swinging the bat well," said Valentine. "We'll see if he can be there if we need him."

Gomez was on Boston's roster from May 11-20, but he had just two at-bats.

It remains to be seen if Gomez will do anything more than pinch-hit during Boston's West Coast road trip. His main position is first base, where the Red Sox already have Adrian Gonzalez.

Third base is where there's a current opening, with Will Middlebrooks day to day with left hamstring soreness. Gomez does have some experience at third, but he hasn't played there since 2009. In 71 Minor League games at the hot corner, Gomez made 31 errors.

"He plays third, we think," said Valentine. "We're going to find out. He signed as a third baseman. He played a lot of third base growing up and has been taking third-base grounders all year."

Mortensen optioned; Germano likely to join 'pen

OAKLAND -- Right-handed pitcher Justin Germano has all but officially joined the Red Sox.

Clayton Mortensen was optioned to Triple-A Pawtucket after the Red Sox's 3-2 loss to the A's on Tuesday and Germano will be added to the active roster prior to Wednesday's series finale.

Germano, 29, exercised the opt-clause in his Minor League contract Monday, and the Sox needed to add him to the 25-man roster or risk losing him to another club. In 17 appearances (16 starts) with the PawSox, Germano was 9-4 with a 2.40 ERA, 72 strikeouts, 13 walks, and 15 home runs allowed in 105 innings.

"I know there are a lot of teams hurting for pitching right now and a lot of teams have lost guys and guys who aren't performing well, so I know there's opportunity out there, whether or not they're interested in me is the big question," Germano told ESPNBoston.com. "I'm still part of the Red Sox organization, and that's my priority right now. I'll deal with them and see what happens, and if they don't have a spot for me, we might have to see what's out there."

Germano's spent parts of six seasons in the Majors, most recently with the Indians from 2010-11. Lifetime in the Majors, he's 8-20 with a 5.02 ERA in 253 innings and 79 appearances, 36 of them starts.

The Sox don't need to clear a spot on the 40-man roster, as they designated outfielder Darnell McDonald for assignment on Saturday and placed Bobby Jenks on unconditional release waivers after reaching a contract termination settlement with the reliever on Tuesday.

After surrendering just one run on five hits and throwing 71 pitches in a five-inning relief appearance on Monday, it was unlikely Mortensen could have pitched until at least Friday.

Valentine shuffles rotation leading into All-Star break

OAKLAND -- Manager Bobby Valentine made some adjustments to his pitching rotation, bumping Aaron Cook up to Wednesday, when he will pitch the finale of this seven-game road trip against the Oakland Athletics.

Cook, coming off a two-hit masterpiece against the Mariners, moves ahead of Franklin Morales, who has also pitched exceptionally well since moving into the rotation.

The reason the Red Sox are holding back Morales from a start until this weekend is so he can be available out of the bullpen Tuesday and Wednesday against Oakland. Lefty reliever Andrew Miller has been used a lot of late.

With the Yankees coming to Fenway Park this weekend, the Red Sox will open with Josh Beckett on Friday night. Morales and Felix Doubront will split the doubleheader on Saturday. Jon Lester gets the Sunday night finale, the last game before the All-Star break.