TOKYO -- The Red Sox finalized their 25-man roster prior to Tuesday's season opener against the Oakland Athletics, and there was one mild surprise.

First baseman Sean Casey, who suffered a stiff neck from sleeping in an awkward position on the flight, will be active for the two games in Tokyo.

Twenty-four hours earlier, the Sox -- who have three inactive spots for the two games at Tokyo Dome -- were expected to leave Casey as a spectator. But the left-handed-hitting first baseman, who will back up Kevin Youkilis this season, improved overnight.

"As long as Casey is OK, he should be on our team," said Sox manager Terry Francona. "He'll be able to pinch-hit or go into the game."

As a result of Casey being active, the Sox optioned catcher Dusty Brown to Triple-A Pawtucket. Brown will remain with the team for the remainder of the trip to Tokyo.

In a move that was already in the works, ace Josh Beckett was placed on the 15-day disabled list, retroactive to March 19, with a lower back strain. Beckett is recovering nicely in his rehab in Fort Myers, Fla., and is eligible to be activated on April 4, when the Red Sox play their fifth game of the regular season in Toronto.

Francona did not rule out the possibility that Beckett might pitch in Toronto.

"I hope so," Francona said. "I'd be OK with that. If that's the way it works, that would be great. Only if it's supposed to happen. We're not going to force it. But that would be great."

With Casey now in the mix, knuckleballer Tim Wakefield and reliever Mike Timlin (stitches on right ring finger) have been designated as the two inactive players.

Bobby Kielty and infielder Jed Lowrie have been classified as extra players and won't be permitted to be in uniform. The Sox were allowed to bring 30 players to Tokyo.