The right-hander told reporters hours before Thursday's game with the Texas Rangers that he feels 100 percent, but the club still needs to see how he responds to a longer outing Saturday, when he pitches for Triple-A Pawtucket in Syracuse.
Beckett will throw around 85 pitches in the start, his second for the PawSox, as he rehabs from a lower back strain.
"This is about as good as I've felt in eight weeks," Beckett said when asked how he responded to a four-inning outing for Pawtucket on Sunday.
Manager Terry Francona indicated that the Red Sox will wait and see before making any rash decisions on Beckett.
"If he's ready to come back and pitch for us, he will. If he's not, he'll get another one," Francona said. "If all goes terrific, he'll come back and take his slot with us."
Beckett first had back issues after a start at Fenway in which he gave up nine runs on nine hits in just 5 1/3 innings against the New York Yankees on May 7. The Sox skipped his next start and then pitched him at a soaking wet Yankee Stadium on May 18.
The 30-year-old Beckett gave up five runs — three earned — in 4 2/3 innings in that game but left after reinjuring the back when he slipped on a delivery to Alex Rodriguez.
He threw 68 pitches in his first rehab start for Pawtucket, allowing a solo homer, striking out four and walking none.
Clay Buchholz will pitch Friday at Syracuse. That is expected to be his only rehab start as he works his way back from a hamstring strain.
