Baylor quarterback Bryce Petty has two cracked small bones in his back.
Petty had an MRI on Monday, a day after taking an early shot to his back and playing only the first half of the 10th-ranked Bears' season-opening 45-0 win over SMU.
The diagnosis was two cracked transverse processes, small bones that stick out from each side of a vertebra.
Coach Art Briles said during the Big 12 coaches teleconference that Petty was day to day. Baylor, which didn't practice Monday, is home Saturday night against Northwestern State.
Petty was hit in the back on his first series Sunday night. He still threw for 161 yards and two touchdowns, and added a 5-yard TD run for a 31-0 halftime lead.