The right-hander played long toss in the outfield earlier Saturday and is scheduled to throw a bullpen session on Monday in preparation for his next start.
"Great. He really felt good today," Valentine said.
Beckett was removed from Tuesday's game against the Detroit Tigers with two outs in the top of the third inning after suffering back spasms while pitching on a wet mound at Fenway. He was skipped from his scheduled start on Sunday against the Minnesota Twins, with left-hander Franklin Morales getting the nod.
Beckett is 5-9 with a 4.54 ERA in 18 starts this season.
Also, Red Sox center fielder Jacoby Ellsbury was scratched from the lineup Saturday because of a leg issue, according to Valentine. Ryan Kalish led off and played center field for the Red Sox, who lost to Minnesota 6-4.
"I'm just being safe with Jacoby," Valentine said before the game. "He has a very little situation that he wanted to play through, and with the day game tomorrow, I vetoed it. Ryan's healthy and ready to go.
"It's a leg issue, but it's not an issue. But it could become an issue."
Ellsbury returned to the lineup on July 13 after missing the majority of the season with a shoulder injury. He's hitting .259 with one homer and six RBIs in 27 games.