Martinez felt pretty well catching Tim Wakefield's knuckleball before Thursday's game, but Buchholz's increased velocity will be a better test for his thumb.
If the session with Buchholz goes well, Martinez's return could be imminent, perhaps as soon as the three-game series in Anaheim that starts Monday night.
"I mean, if I feel like I felt yesterday with Buchholz, I'm just days away," Martinez said. "We'll see what happens."
The Red Sox have been forced to play with both of their regular catchers on the 15-day disabled list. Jason Varitek has a fractured right foot and is still on crutches. The return of Martinez would give the Sox a big jolt in the middle of the lineup.