Sweeney still hasn't been cleared to play, and manager Bobby Valentine said after Monday's 8-6 win over the Orioles that Sweeney could go on the seven-day disabled list that was instituted specifically for players who suffer head injuries.
"I don't know how bad it is," said Sweeney. "I did some of the tests today, and I think I did OK on the reaction stuff. They said when you have something like this, and you overexert yourself and try to do too much, you've got to let your head heal. I did some hitting and some bike, and just kind of felt a little tired today. I've just got to come in tomorrow and see how I feel."
With Cody Ross set to go on the disabled list with a fracture in the navicular bone of his left foot, the Red Sox can't afford to carry Sweeney on the roster if he's unable to play.
Sweeney felt whip-lash symptoms after making a sensational catch on Saturday night against the Phillies. With Sweeney and Ross both out, Che-Hsuan Lin added a hit and a run in his first Major League start.
"I've never had anything happen to my head before, so I don't really know," Sweeney said. "As a player, you want to go out there and play, but sometimes it might not be the smartest thing to do. You've got to watch out for your health."