The running back was drafted by the San Francisco 49ers last year, but spent his rookie season on the sidelines while recovering from a serious knee injury.
The defensive end, who is projected to be one of the top picks in this year's Draft, told reporters: "The guy is a hard worker. This guy comes to work every day. He pushes himself and pushes the team.
"He's a competitive guy, he wants to be great just like everybody else playing this game. Marcus Lattimore is one of the great backs in South Carolina history and hopefully he'll show that in the NFL."
Clowney has been taking part in the Scouting Combine in preparation for the Draft.