"There was no bleeding or damage, but it was a preliminary report," Francona said. "I wasn't really comfortable playing him tonight. He may be available to pinch hit [tonight] and play tomorrow. That would be the best case. I just didn't have a really good feeling running him out there. Knowing the way he plays, I don't want him to hurt himself."
Beltre, who suffered a left-hamstring strain when he grounded out to shortstop Sunday in Toronto, played briefly in his first All-Star Game and was scheduled to run and take BP at Fenway Park on Thursday.
"It's not as bad as people thought," Beltre said. "It's just a mild strain, so in a couple of days I should be ready to go."
Beltre was ready to play against the Rangers on Thursday, but Francona and the medical staff are being cautious. Beltre received treatment earlier in the day and is trying to strengthen the hamstring. He said he's had similar hamstring issues "many times" during his career, especially one particular blowout during the 2000 season when he was with the Dodgers. He believes he'll be able to manage it this time around because it's not as bad.
He explained this injury feels more like a cramp, whereas the one he suffered in 2000 felt like someone "shot him in the leg."
Beltre did say he was a little nervous prior to the MRI.
"You never know what they'll find in there," he said. "It wasn't a nice feeling after the ground ball on Sunday. I was hoping everything was fine and it's something I can manage."
Beltre and the Sox will wait to see how he feels in the morning before making a decision whether the third baseman will be back in the lineup on Friday.
His All-Star experience was an interesting one, too.
After suffering the injury in Toronto, Beltre said he would likely still be able to play in the All-Star Game, but there was some miscommunication with AL manager Joe Girardi, who said at a press conference he was replacing Beltre on the roster with the Rangers' Michael Young.
"I was shocked because no one told me anything," Beltre said. "Maybe if somebody talked to me and said, 'We would rather you not play?' Maybe I would have said it was a good idea. But to take the initiative, saying I'm not on the roster without talking to me, I don't think that was the right thing to do. I don't care anymore. I had fun. I got my at-bat. It's not a big deal. It's in the past."
Joe McDonald covers the Red Sox and Bruins for ESPNBoston.com. Follow him on Twitter.