Matsuzaka, who suffered a mild strain of his right rotator cuff in his May 27 start against the Mariners, threw on flat ground after pitching coach John Farrell said the star right-hander tested out of his shoulder strengthening regimen on Friday.
"Tested out fine again [Friday], so that mean's we've got clearance to initiate the throwing program," Farrell said. "I think a lot of it will depend on how he progresses."
Farrell said Matsuzaka would begin throwing at 60 feet the first day.
"That's pretty consistent to all of our pitchers coming back in a situation such as this," Farrell said Friday. "So we'll begin at that distance and progress to long toss. There will be a minimum of one, likely two bullpens before putting him back in the game."
Sox manager Terry Francona said the workout prior to Boston's Saturday matchup with Seattle was strong.
"Everything went well," Francona said. "He's officially onto his throwing. Flat ground; it'll be flat ground for a while. This should come along pretty quickly."
He said the team will evaluate whether it's in Matsuzaka's best interest to remain with the team until he returns to the mound or to send him down for a rehab assignment with Triple-A Pawtucket.
"Does he need to go down? I don't know. I honestly don't know," Francona said. "If it's in his best interest; I'm sure we'll sit down and talk about it and include Daisuke, and try to figure out what's in his best interest."
Prior to his stint on the disabled list, Matsuzaka led the American League in wins with eight. He remains 8-0 in 11 starts with a 2.53 ERA on the season.
But even though Matsuzaka is back to throwing, it is still unlikely he'll be able to make a quick return. He's scheduled to come off the disabled list on June 12.
"Yeah, that's a little quick," Francona said.
Mark Remme is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.