"From talking to [assistant trainer] Mikey [Reinold] today, I don't think there's an injury," Francona said. "It looks like he's got some fatigue. Kind of like last year, where he's got to build it back up and feel good about himself. I don't think today he felt real good about himself."
Matsuzaka was placed on the 15-day DL last May 28 with a mild right rotator cuff strain. He missed three weeks.
Though Matsuzaka denied any physical issues in his briefing with reporters on Tuesday, Francona said the pitcher was on board with the move to the DL.
"[General manager] Theo [Epstein] and I had talked last night and this morning, and contrary to what Dice-K said last night, he understands it," Francona said. "I think sometimes guys say things when they're in the [heat of battle], trying to compete. We just want him to be able to be Dice-K, not part of Dice-K. We'll put him on the DL, we'll have him looked at Friday, and then we'll put our heads together and see what's the best way we can get him to make all his starts and be good."
Matsuzaka gave up five hits and five runs over one inning in his abbreviated start on Tuesday, walking two, striking out none and throwing 43 pitches.
"It's still early in the season, so I want to take this in a positive light," said Matsuzaka. "I respect and appreciate the ballclub's decision to give me time to deal with my fatigue, and I'm going to do everything I can to get back to where I need to be as soon as possible. I'm glad it's early and the only thing I can do is move forward."
Left-handed reliever Hunter Jones was summoned from Triple-A Pawtucket on short notice and flew to Oakland to take Matsuzaka's spot on the roster.
Who will take Matsuzaka's spot in the rotation? Francona didn't have an answer for that yet, but there's a strong possibility Justin Masterson will fill the void. The right-hander fired four shutout innings in relief of Matsuzaka on Tuesday and was stretched out as a starter during Spring Training.
"I think, 17 days ago, he threw 80 pitches," Francona said. "And then last night he got stretched out a little bit. Certainly that's an option. We'll see."
Matsuzaka, who went 3-0 in helping Team Japan win the World Baseball Classic, is 0-1 with a 12.79 ERA in two starts.
"He's coming off of a [situation] where he's pitching his heart out with a lot of emotion, then he comes back to a Spring Training game," said Francona. "I think it's somewhat, maybe, expected. This is why we like to keep our eyes on guys all spring and watch them build up so we can watch the progression. It's frustrating. And we knew it going in, we talked about it. It's there. [We'll] deal with it the best we can. We've had a tough week to boot. Now we lose a pitcher. We're not thrilled about it. But what are you going to do?"