"I wanted to show the manager and the coaching staff that I am ready to pitch in a game situation, and I feel I did that," Matsuzaka said.
With Matsuzaka rejoining the rotation, a starter had to be moved to the bullpen. That starter is Tim Wakefield, who hasn't pitched in relief since 2004. He will be available in the bullpen, starting Friday.
"I have a lot of respect for what Wake has done and for what Wake will continue to do," said Francona. "Again, this is not us turning him into a reliever. This is us putting him in the bullpen until he starts again."
Matsuzaka said that he has been "a burden" and "a distraction" to the club because of his time on the disabled list.
"I don't want to be any further distraction," Matsuzaka said through an interpreter. "I think it's always my goal to try to pitch efficiently and go through as many innings as possible. That's the focus as I go through my workouts. I think right now, when it comes to actually guiding the ball itself, I have a really good feel for the ball.
"I think the reality that I'm back with the team won't hit me until I'm actually on that mound. I think I will be really nervous when I first go out there."
Pitching coach John Farrell was also impressed with Matsuzaka's performance.
"His cutter and slider were tight, powerful and that's an indication of increased arm strength," Farrell said.
Matsuzaka was limited to 12 starts last season as he spent time on the disabled list with a shoulder strain. But he finished strong in his final four starts, going 2-1 with a 2.22 ERA.
Farrell was asked to compare what he saw from him Monday with the way Matsuzaka finished the season.
"Until we get against Major League hitters in a Major League game, we'll see that more clearly." Farrell said. "But given where he was earlier in Spring Training, it's a noticeable difference today than five starts ago. Using the one game in Washington [on April 3] as a comparative, [Matsuzaka was] much more sharp, much more clean with all four pitches that he threw today."
Farrell said that Matsuzaka worked hard in the offseason.
"The work that he did in the offseason, he was clearly committed to a rigorous program even though he was delayed," said Farrell. "I think there was disappointment that he was not able to start on time. But his work and how he's gone about it has been very consistent, from the time he came back last year and throughout the offseason and in Spring Training."
Francona said that Matsuzaka got up to about 100 pitches on his rehab assignment.
"[Saturday] would be like his first start of the season, so you're not going to see 120 [pitches]," Boston's skipper said. "I think as far as arm strength goes and everything, he's in pretty good shape."