Triple-A Pawtucket manager Ron Johnson, for whose team Beckett started, liked what he saw from the pitcher.
"He looked good. He felt good. Everything was good," Johnson said.
"The thing I really liked is he approaches it the same as if he was pitching at Fenway Park. He's high-fiving the guys when he came off the mound. It's good for the young guys to see that."
Beckett, who was 20-7 with a 3.27 ERA last season, has no timetable for a return to the big league team, which is currently in Japan preparing for its season-opening set with the A's that begins Tuesday in Tokyo.
"You can't really [put a schedule on it]," Beckett said. "It's just one of those things. You just go out there and you feel good every day and progress yourself back. I think [Sunday] was just a good mental hurdle to get over to prove to yourself that your back's not hurting. So I crossed that, and now we can get into the building-up stage."
Although he has made progress, Beckett said it is a possibility he could start the season on the disabled list -- as Sox manager Terry Francona suggested earlier.
"Absolutely, I think that's possible," Beckett said. "I think that's been a possibility the whole time. [But] I don't know. I think that's kind of what everybody was preparing for. ... There's just no sense in going out there and trying to kill yourself to get back to that April 1 start when really you've only thrown seven innings. I probably need 14 more innings down here, and then I'll be prepared."
Beckett said he learned after the 2003 season, when the Marlins won the World Series and he was the Series MVP, that the shortened offseason has its effects.
Beckett made three trips to the disabled list in 2004, first with a blister on his right middle finger May 31. Then, a day after returning to the roster he was placed on the DL again, June 18, with a strained lower back. Then, a day after returning, July 6, he went on the DL again with a skin tear on his right middle finger.
"I threw a lot of innings in October last year. I threw a lot of innings in '03, [and] '04 wasn't exactly a healthy year for me," said Beckett. I'm not saying that this year is going to be like that, but you got to prepare a little bit different because you don't have that full offseason to work it out."
And it's part of the reason Beckett is proceeding cautiously with his current back injury.
"I think [the shorter offseason] definitely could have played a role in [the back injury]. ... This is such a freak deal for me, because I've never had any back issues at all," he said.