Ash, who started 12 games for the Longhorns last season, suffered a concussion in a game against Brigham Young University on Sept. 7. He missed the following game against Mississippi and left the Sept. 21 game against Kansas State at halftime, experiencing symptoms of a head injury, the San Antonio News-Express reported.
"Though he's made a lot of progress, we have not been able to clear him to return to competition," head athletic trainer Kenny Boyd said.
Ash is expected to return for spring practice. If he is granted an extra year of eligibility, he will play next season as a junior, the newspaper said.