STILLWATER, Okla. -- Colorado quarterback Tyler Hansen has returned after leaving the Buffaloes' game at No. 12 Oklahoma State with a right thumb injury.

Hansen went to the locker room for X-rays midway through the second quarter, but came back to start the second half. After a muffed punt by Oklahoma State's Perrish Cox, he threw a 28-yard touchdown pass to Markques Simas to give Colorado a 21-10 lead.

Hansen broke the thumb during Colorado's spring game when he slammed it into another player's helmet.

Cody Hawkins, the Buffaloes' starter at the beginning of the season, replaced Hansen in the second quarter and led a go-ahead scoring drive capped by his 5-yard touchdown pass to Riar Geer.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

STILLWATER, Okla. (AP) _ Colorado quarterback Tyler Hansen has left the Buffaloes' game at No. 12 Oklahoma State with a right thumb injury.

Hansen was sacked three times in the first quarter and had a 4-yard rush on the series before he walked off the field and toward the locker room midway through the second quarter.

A team spokesman says X-rays on Hansen's thumb came back clear but his return is questionable. Hansen broke the thumb during Colorado's spring game when he slammed it into another player's helmet.

Cody Hawkins, the Buffaloes' starter at the beginning of the season, replaced Hansen on Colorado's next drive. He threw a 5-yard touchdown pass to Riar Geer to give Colorado a 14-10 halftime lead.