SEATTLE -- Daisuke Matsuzaka was to return to Boston for more tests on his fatigued pitching shoulder, leaving at least his next start in jeopardy.
The 11th Red Sox pitcher to win his first eight decisions in a season left his start in Seattle on Tuesday after four innings. He threw two seemingly routine warm-up pitches before the bottom of the fifth, then departed with what the Red Sox continued to vaguely term Wednesday as "shoulder fatigue."
Matsuzaka's chance to join Josh Beckett as the second Red Sox pitcher since 1971 to begin a season 9-0 is on hold while he awaits an MRI on Friday. The rest of his teammates will be in Baltimore that day to begin a four-game series that Matsuzaka is still, for now, scheduled to finish on Monday.
"We are going to send him back to Boston for a precautionary MRI," Red Sox manager Terry Francona said after emerging from behind a clubhouse office door that was closed for more than an hour while he met with Matsuzaka, the team's training staff and interpreters.
The team wants its doctors, led by medical director Dr. Thomas Gill, to review the MRI results before deciding what to do next with the AL's co-leader in wins entering Wednesday.
"If we are going to err, it is going to be on the side of caution," Francona said. "We're not forgetting who we are dealing with. We are dealing with a guy who is one of the best pitchers to ever come out of Japan. That's why we signed him."
Francona refused to assume Matsuzaka would miss his start against the Orioles. As Francona was talking in the dugout, Matsuzaka gently flipped a few balls overhand about 20 feet while standing near a screen in the outfield during batting practice.
"I wouldn't assume anything," Francona said. "We have time. We don't have to decide yet.
"The word I used [Tuesday] night was 'fatigue.' I think that's the proper word. If it's vague, we're not trying to be. Putting your hand on someone's shoulder and examining it is not an exact science."
Matsuzaka said after Tuesday's game he wasn't concerned with his shoulder issue. On Wednesday, he did a series of strength tests with trainers. Assistant trainer and team rehabilitation coordinator Mike Reinold then compared those results to baseline tests Matsuzaka took in spring training.
"Actually, he tested out pretty good, which we were pleased" about, Francona said.
Boston gave Matsuzaka a $52 million, six-year contract, after paying $51.1 million for the right to negotiate with the right-hander who was 108-60 with a 2.95 ERA in eight seasons with Seibu of Japan's Pacific League. He went 15-12 with a 4.40 ERA for the Red Sox last season and had been on track to perhaps start the All-Star Game for the AL on July 15.
Then came Tuesday, when he said he felt "off" in the bullpen before the game and then throughout his four innings in which he allowed three runs -- two earned.
"I wasn't at my best. After pitching the fourth inning, I definitely felt there was something wrong, and I had a conversation with the coaching staff," he said through an interpreter late Tuesday. "I went out for the fifth inning to give it a try, but felt it was best to stop there.
"With so much of the season left, I thought that it would be best to come out of the game at that point."
Matsuzaka was unavailable for comment Wednesday.
"The good news is he showed up today and said he felt pretty good," Francona said, adding he did not believe Matsuzaka felt pain in his shoulder at any time Tuesday.