"He took it pretty flush, from what I heard," Cubs manager Mike Quade said. "It's something that's dangerous enough that they're going to take a good look at it."
The Cubs, who rallied to beat the Red Sox 9-3, did not expect an update until Sunday.
With one out in the second and the count 1-2, Byrd was struck by a pitch, and he dropped to the dirt. He was writhing in pain -- and grabbed his face. He was able to walk off under his own power but had a bloody gash under his eye.
He never lost consciousness. Byrd was taken to Massachusetts Eye and Ear Infirmary to be examined.
"You could see he was scrambling and kind of panicking because he doesn't know what's going on," Cubs outfielder Reed Johnson said. "I know whatever he can do to get back sooner, he'll do. He'll probably end up coming back sooner than we think. Hopefully, everything will work out all right."
Aceves said after the game that the beaning was unintentional. He said he tried to find out how Byrd was doing but hadn't heard, saying he was concerned.
"There's nothing you can do about a walk or a hit by pitch," Aceves said. Nothing intentional, obviously."
It's the 13th time a Cubs player has been hit by a pitch since May 6, and the fifth time Byrd has been plunked since May 11. He was hit twice on Friday.
"I came up every inning when I was pitching and asked the trainer how Marlon was, and he said he's at the hospital," Cubs pitcher Carlos Zambrano said. "I'll put him in my prayers."