BOSTON -- The A's, in need of as much bullpen help as possible following Saturday's five-plus hour game vs. the Red Sox, elected to designate infielder Andy LaRoche for assignment on Sunday morning when they reinstated right-hander Grant Balfour from the paternity leave list.

The move means the A's are without an extra infielder, though Adam Rosales is expected to join the club soon barring any setbacks in his rehab assignment with Triple-A Sacramento following nearly six months of nursing his surgically-repaired right foot back to health.

"I was surprised," LaRoche said. "I didn't see it coming, but with Rosales coming off the disabled list, they were going to have to make a decision quick. With the game yesterday, they needed an extra pitcher, so I guess they can do all right for a couple of games without an extra infielder until Rosales comes back."

LaRoche, 27, was batting .247 with five RBIs in 40 games. He started 28 games at four different positions, including 17 at third base, after beating out Eric Sogard for the utility job out in Spring Training.

The A's, who now have an open spot on the 40-man roster, have 10 days to either place LaRoche on waivers, trade or release him.

"Obviously there were a lot of things that I could have done better," he said, "but I was happy with the opportunity to get to play all of the positions. I got a lot more playing time than I was expecting. Now I'll just see if another team out there needs me.

"I would obviously prefer to be in the big leagues, and if that's not here, hopefully it's with another team. If there's not that need, then I'll probably be in [Triple-A] Sacramento."

For the time being, manager Bob Geren said Kevin Kouzmanoff would play at shortstop or second base in the event Cliff Pennington or Mark Ellis was unavailable, and Conor Jackson could fill Kouzmanoff's place at third base.

"Obviously we needed the pitching today," Geren said. "Andy played all the positions and did a fine job of what we asked him to do."

Balfour activated off paternity leave list

BOSTON -- The A's welcomed back a familiar face with open arms on Sunday, reinstating right-handed reliever Grant Balfour from the paternity leave list.

Balfour represents one of just a handful of pitchers available out of the bullpen for the club's series finale against the Red Sox following Saturday's 14-inning contest.

A's manager Bob Geren said his available arms include Balfour, along with lefty Craig Breslow and right-handers Fautino De Los Santos, Brad Ziegler and possibly Michael Wuertz.

"A win in nine would be best," Geren said, smiling.

Balfour, 33, and his wife, Angie, welcomed their first child on Thursday night. Daughter Raegan Madison Balfour weighed in at 6 pounds and 10 ounces and is 20 1/2 inches long.

As of Sunday, the right-hander was tied for third among American League relievers in wins (three) and had posted a 2.92 ERA in 25 relief appearances, striking out 28 along the way.

Willingham out of lineup with sore Achilles

BOSTON -- Outfielder Josh Willingham has been deemed day to day after aggravating his left Achilles tendon during Saturday's 14-inning game against the Red Sox.

Willingham's absence from Sunday's series finale, combined with the team's decision to designate Andy LaRoche for assignment, meant the A's had only two bench players available in Hideki Matsui and Landon Powell -- the former whom Geren said could play in the outfield if need be.

The 32-year-old Willingham has represented the club's biggest run producer, batting .304 with five doubles, four home runs and 14 RBIs over his last 13 games. Overall, he's batting .249 with 10 homers and 39 RBIs and is hitting .362 with runners in scoring position this season.

Willingham, who missed a couple of games earlier in the year because of back tightness, is coming off a 2010 campaign in which he played in just 114 games before watching his season come to a premature end following left knee surgery.

Worth noting

• The A's are still considering starting right-hander Guillermo Moscoso in Baltimore on Tuesday, even though he pitched in relief on Friday and Saturday. Another option, manager Bob Geren said, is moving up Josh Outman and having Moscoso throw on Wednesday. Outman threw just 67 pitches in his last start on Friday.