Tests done on Monday at Fenway Park did not reveal any structural damage.
"He's day to day right now," said Red Sox manager John Farrell. "Obviously the sprain to the left shoulder [happened] on the collision. We're hopeful over the next couple days there's some improvement. There's no clear-cut DL at this point. So he's day to day."
"A bit sore, but back soon. Hang in there #RedSoxNation, and thanks for all the prayers," Ramirez said in a tweet.
Ramirez is hitting .283 with 10 homers and 22 RBIs while making all but one of his starts in the cleanup hole.
"It's a tough one," said shortstop Xander Bogaerts. "He's been one of our most productive hitters so far. Losing a big player like that would be tough."
The Red Sox are fortunate to have depth in the outfield, even though Shane Victorino is on the disabled list for another week.
Allen Craig has been an everyday player for most of his career but was without much of a role on this team. He can give the Red Sox a threat in Ramirez's absence. Daniel Nava and Brock Holt can also step in.
Rusney Castillo is just getting back on his feet at Triple-A Pawtucket after coming back from a shoulder injury of his own, so the Red Sox likely wouldn't call him up at this point.
In the first inning on Monday, Ramirez injured his shoulder while attempting to catch a hard James Loney liner to left field. He momentarily trapped the ball in his glove before a collision with the left field sidewall jarred it loose.
Ramirez was shaken up and crouched down on the field for several moments while members of the Red Sox training staff surrounded him. He eventually walked back to the dugout under his own power and was replaced by Craig in left field.
Shoulder woes have dogged Ramirez in the past. He underwent arthroscopic surgery on his left shoulder at the end of the '07 season. In '11, Ramirez suffered a left shoulder strain that kept him out for the final two months and necessitated surgery.
"Based on the exams and the images tonight," said Farrell, "I don't have anything that suggests there's a reoccurrence of an old injury. I think over the coming days, we'll have a read on how he can recover, and we're hopeful he won't miss significant time."
"I promise, gonna try to be back as soon as I can," Ramirez tweeted.
It was a tough play for Ramirez, in that he simply ran out of room in the corner.
"He's been on a roll at the plate," said Clay Buchholz. "I thought it was worse than it turned out to be, which I guess is a good thing."