Josh Beckett just has one more test to pass before returning to the Red Sox’ rotation – an extended side session Tuesday.

If Beckett comes through Tuesday’s session in good shape, the plan is to have the righty pitch Friday in Seattle against the Mariners.

“As far as the build-up and stuff, I think I’m where I need to be,” Beckett said after the Red Sox’ 4-2 loss to the Rangers Sunday afternoon at Fenway Park. “Obviously, I can’t make that decision all by myself. We’ll just have to see where it goes from there. As far as I’m concerned, yeah, I’m ready to start on Friday, but it’s not the be-all, end-all.”

Beckett is coming off a rehab outing for the Pawtucket Red Sox in which he allowed three runs on five hits over four innings against Syracuse. In all, the Sox’ hurler has made three rehab starts, two for the PawSox, and one a simulated game against Gulf Coast League hitters.

“Really good,” said Beckett when asked about his analysis of Saturday’s start. “I actually thought the worst inning was the best I felt in terms of the way I was throwing and stuff like that.”

Regarding what he wants to get out of his side session Tuesday, and how it might be different from a normal in-between-start bullpen session, Beckett explained, “It’s just making the adjustments from pitch to pitch instead of taking two or three pitches to make the adjustments.”

If Beckett does pitch Friday, it will be 72 days since he last took the mound, when he re-injured his back on May 18 in Yankee Stadium.