Manager Fredi Gonzalez said Hanson's car blew a tire while he was going around a corner on a street near Champions Stadium at Disney's Wide World of Sports complex in Florida.
"He bumped his head, on the windshield or the steering wheel. (We're) not sure which," Gonzalez said. "So with all the concussion (issues) now, we've got to make sure he's fine."
Gonzalez said it's possible Hanson could be out for a day or two, depending on what the concussion testing reveals.
Jayson Stark is a senior baseball writer for ESPN.com.