Clowney departed practice early after colliding with Broncos tight end Jacob Tamme during a 9-on-7 drill. Clowney sat in the tent for the remainder of the team's joint practice, but it didn't appear he was being examined by trainers while he rested.
Clowney felt OK afterward, according to a source, but the team wanted him to undergo additional testing.
Texans coach Bill O'Brien said after practice he didn't know what Clowney's situation was.
Houston drafted Clowney first overall out of South Carolina in May. He began showing his ability almost immediately in practices and workouts. Clowney had sports hernia surgery in June, but was healthy enough to return to practice a few days into training camp. Periodically, the Texans have given Clowney days off to manage his return.
Wednesday's issue did not appear to be related to his sports hernia surgery as Clowney's gait did not seem affected.