Walsh, a junior, was injured during the first quarter of the Cowboys' win over Missouri State last Saturday, and was later seen on the sidelines with his ankle wrapped and on crutches.
Earlier Thursday, KFOR.com reported that Walsh had surgery on his lower leg/ankle and would be out six to eight weeks.
A team spokesman told the World that Oklahoma State wouldn't comment on the situation. Oklahoma State head coach Mike Gundy hasn't addressed Walsh's status, other than saying Monday he'd remain in a walking boot and be re-evaluated Tuesday.
In Oklahoma State's season opener against Florida State, Walsh passed for 203 yards and a touchdown and rushed for two more scores.
Daxx Garman replaced Walsh against Missouri State. He went 16-for-26 with 244 yards and two touchdowns.
The Cowboys play Texas-San Antonio on Saturday.
- Molly Geary