"It feels a lot better today," Beckett said Saturday, addressing reporters for the first time since he returned to Boston on Tuesday to see foot specialist Dr. George Theodore, who confirmed the original diagnosis of a sprained right ankle. "Two days ago it was pretty rough."
Beckett said he has fluid in his ankle in the back of the joint. The ankle ligament was not damaged, he said, because he severed the ligament when he sprained the same ankle "when I was in middle school."
"This is where the pain is coming from," Beckett said. "I had fluid in my joint. When you have fluid in there it takes up space and when you do certain movements it pinches you. That's what I'm getting."
Beckett said the ankle was able to handle his body weight pushing off on Saturday. The next step would be to throw off a mound. He agreed it's reasonable to expect that he would do so by midweek, which would put him on track to start by next weekend.
"It's not my decision," he said. "I think the trainer has got to be comfortable with where I'm at. I don't see it being too much longer.
"This thing needs to be 100 percent or at least close to 100 percent whenever I come back because it makes everyone look foolish if you go back out there and hurt it five pitches in. I don't think we're going to do that. We're going to test it off the mound first and figure things out."
Red Sox manager Terry Francona wouldn't commit to a timetable for when Beckett would resume throwing off a mound.
Beckett said he has maintained arm strength by doing shoulder exercises and throwing a ball against a wall.
"Arm strength is not a real issue," he said. "We're going to take it day by day. If I come in tomorrow and it's flared back up, this was all for naught."
Beckett came out of Monday's game in Toronto in the fourth inning. He said he's still not sure how the injury occurred, that it could have been related to his fall in the bullpen while warming up, but the doctor was unable to pinpoint the cause.
He acknowledged that he initially thought the injury was serious.
"When I first came in it hurt bad," he said. "I thought it was the Achilles because of where my pain was. It was in the back of my foot. That's where the fluid is trapped and we got to get rid of that. It could be one start. That's the best-case scenario, but obviously it's not my decision."
Beckett said he expects that Theodore will want to take another look when the team returns to Boston.
"It's not on my schedule," he said. "I'm sure it's on his."
Meanwhile, left-hander Erik Bedard, who has a lat muscle strain, has not yet resumed throwing.
"He's improving," Francona said. "The one thing we don't want to do is try to rush him back. The timetable isn't really set in stone. It's how he feels, and I don't think he thinks he needs a whole lot (of time) once he feels good."
John Lackey has a sore left calf after being hit by a batted ball during his start Friday night. The Red Sox believe the right-hander could make his next scheduled start on Wednesday.
Nonetheless, Francona acknowledged the idea of putting Alfredo Aceves in the starting rotation has been discussed, but the manager continues to maintain that would leave the Sox with too big a hole in their bullpen.
"We've talked about it," Francona said Saturday, a day after Lackey lasted just three innings and gave up five runs, his ERA climbing to 6.30, the highest among all major league qualifiers and almost a full point higher than the runner-up, Brian Duensing of the Minnesota Twins.
"He's a pretty good pitcher, I'll acknowledge that I think he can start for us. I don't know, we're at a point in the season -- again, we may get to the point where we have to do it, who knows?"
Gordon Edes covers the Red Sox for ESPNBoston.com. Information from The Associated Press was used in this report.