OAKLAND -- It appears that Daisuke Matsuzaka's workload leading up to and during the World Baseball Classic has caught up to him.

The Red Sox right-hander labored through just one inning before being pulled from Tuesday night's game in Oakland with what the club diagnosed as arm fatigue.

Matsuzaka threw 43 pitches, only 22 of which were strikes. After being staked with a 3-0 lead before even throwing a pitch, Matsuzaka gave up five hits and five runs in that one inning, walking two and striking out none. He faced 10 batters. Despite 10 shutout innings from the bullpen, the Red Sox lost, 6-5, to the A's in 12 innings.

"We talked to him the other day," Red Sox manager Terry Francona said. "He expressed a couple of days ago some kind of general soreness or fatigue in the back of his shoulder from the [Classic]. We thought we talked it through pretty good in Anaheim and he came out tonight and didn't really have a whole lot. We'll re-evaluate him in the morning."

It was the shortest start of Matsuzaka's career. The only thing close was June 21 of last season when Matsuzaka faced just 12 batters in a loss to the Cardinals -- his first start after coming off the disabled list.

In that game, Matsuzaka came out for the second inning and was pulled after the first three batters reached base.

During much of Spring Training, Francona often said that there was concern that Matsuzaka and the Red Sox might eventually pay the price down the road for the righty pitching in the World Baseball Classic.

Matsuzaka started three games in helping Team Japan defend its title, winning the Most Valuable Player Award in the event. Tuesday's game was Matsuzaka's second start of the season. He wasn't particularly impressive in the first one, giving up nine hits and four runs over 5 1/3 innings against the Tampa Bay Rays.

"Again, I know I'm harping on it a little bit, but I think he probably tried to ramp up too quick [for the Classic] and we're feeling the effects of it," Francona said. "We're eight games into the season, we've lost [six] games, it's not a real fun night."

Matsuzaka seemed perplexed when pressed by the media about his condition.

"I haven't gotten a chance to speak with the manager after the game ended, but for me, personally, I think I'm OK," Matsuzaka said.

Will the righty make his next start, which is currently scheduled for Monday against the Orioles?

"For now, that's my intent, but I won't know for sure until tomorrow when we have those discussions," Matsuzaka said.

If Matsuzaka can't pitch, Justin Masterson is one candidate. The righty, who pitched four shutout innings in relief of Matsuzaka, was stretched out as a starter during Spring Training.

Clay Buchholz, Boston's top pitching prospect, is also just a quick phone call away at Triple-A Pawtucket.