Matsuzaka will officially start his Minor League rehab assignment for Triple-A Pawtucket on Saturday. His second Minor League start on April 15 likely won't be his last.
"No, I think he's going to need a little bit more," said Red Sox manager Terry Francona. "I think he needs to pitch a little bit. I don't think you just need to look at the radar gun, but you need to look at command with a fastball and his offspeed pitches. I think the more he pitches, the better off he'll be."
Matsuzaka pitched four innings out of the bullpen for Boston in Saturday's exhibition game at Washington. He gave up two hits and a run, walking three and striking out one.
Dice-K would have pitched next on Thursday, but due to a technicality, a player who is on the DL can't pitch until a week after he appeared in a game in which admission is charged.
Matsuzaka pitched in two Grapefruit League games this spring and also pitched twice in Minor League games.
When he returns, the Red Sox will have to figure out how to finagle him into a rotation that already includes Josh Beckett, Jon Lester, John Lackey, Tim Wakefield and Clay Buchholz.
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.