This will kick off Matsuzaka's second rehab assignment as he recovers from Tommy John surgery. He had a 4.62 ERA in five starts on his previous assignment, and Red Sox manager Bobby Valentine hinted that the Japanese right-hander wasn't ready for the majors.
Just days before his MLB-limit 30-day assignment was set to end, the Red Sox announced Matsuzaka had received an injection for a strained right trapezius muscle and would not make his last rehab start.
That new injury reset the clock on a new 30-day rehab assignment for Matsuzaka, who last pitched in the majors on May 16, 2011. Technically, the Red Sox could activate him at any time during the new 30-day window, which begins Saturday with his start against the Toledo Mud Hens at McCoy Stadium.
Asked Friday how many pitches Matsuzaka would throw, Valentine said "less than 90, maybe that 75 plateau."
Matsuzaka made no mention of discomfort May 17 following his last start for Pawtucket, in which he gave up five runs in 6 2/3 innings to Durham.
"I feel fine right now," Matsuzaka said through interpreter Jeff Cutler. "Nothing awkward. No pain. I feel good."
During his rehab, there have been indications Matsuzaka still had some work to do after undergoing elbow reconstruction surgery June 10. Customarily, it takes a year to 15 months to recover from the surgery.
Although Matsuzaka has appeared to be ahead of schedule for much of his rehab this spring, his velocity averaged about 91 mph in his last start, according to one observer, and he showed a lack of confidence in both his changeup and curveball.
Valentine has been cautious throughout the process.
"I still haven't wrapped my head around that whole thing," he said May 18. "I really dislike calendars dictating when good health has returned."
Information from ESPNBoston.com's Gordon Edes and Joe McDonald was used in this report.