Tim Wakefield and Daisuke Matsuzaka are making their way back from injury, while the recently signed Paul Byrd is working himself into shape.
Wakefield made his first medical rehabilitation start for Triple-A Pawtucket on Saturday, allowing two earned runs over 3 2/3 innings while striking out three versus one walk.
Wakefield needed 63 pitches, 40 of which were strikes.
"It sounds like he threw the ball well," manager Terry Francona said. "He had a noticeable limp. We don't know if he can field his position yet. We'll try to figure out how he's doing."
Wakefield injured his left calf muscle as he worked to return from a back injury that placed him on the disabled list on July 21, retroactive to July 18.
He is 11-3 with a 4.31 ERA over 17 starts this season.
Matsuzaka is expected to throw another bullpen session on Monday. He threw 65 pitches on Friday, using all of his pitches, and had no complaints after the session.
Francona said Matsuzaka's arm slot was a little inconsistent, but that that was nothing out of the ordinary for someone working himself back into shape.
Matsuzaka has struggled throughout the season, putting up an 8.23 ERA over 35 innings and eight starts. He was placed on the 15-day disabled list with a right shoulder strain on April 15 and returned on May 22.
Matsuzaka was later placed on the 60-day disabled list on June 21, retroactive to the day before. He has missed 82 games so far this season.
Byrd signed with the Red Sox on Aug. 6 after announcing he would join a team toward the end of the season rather than pitch an entire season. He pitched well for the Red Sox last season, posting a 4.78 ERA and four wins over eight starts down the stretch.
Byrd has made two starts for the Red Sox's Rookie League affiliate in Fort Myers, Fla.
On Saturday, he allowed seven hits and six runs (two earned) over four innings. Over two starts, Byrd is 0-1 with a 5.14 ERA over seven innings pitched with the Gulf Coast Red Sox.
Byrd, who is slated to start for Triple-A Pawtucket on Wednesday, hasn't walked a batter and has struck out three.
Junichi Tazawa and Clay Buchholz started their seasons in the Minors, but they are now in Boston's big league rotation. They have combined to go 2-3 with a 4.10 ERA over 37 1/3 innings.
Tazawa started Sunday's game against the Rangers, a team the Red Sox led entering Sunday by just a half-game in the American League Wild Card race.
A decision will also be made concerning John Smoltz on Monday. Smoltz has already said he would not accept a demotion to the Minor Leagues, which means the Red Sox will either have to trade him by then or outright him.
Daniel Paulling is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.