Panthers coach John Fox said Smith and Lucas returned to Charlotte after the fight. The team didn't provide an update on the extent of Lucas' injuries, and club officials declined to say if the volatile Smith, the team's top receiver, would be suspended.
"We're going to handle this matter internally," general manager Marty Hurney said.
Smith's agent, Derrick Fox, did not immediately return a phone call seeking comment.
The melee came after both players had taken off their helmets in a break for starters during a special teams drill. It was unclear what provoked the fight. While the two have routinely jawed at each other in practice since Lucas signed with Carolina in 2005, they've never come to blows in view of reporters.
When attention turned from the field to the fight, several players and Fox rushed to the scene. Fox tried to separate the two, but it took linebacker Jon Beason to pull Smith off Lucas.
Lucas walked to a tent, holding his head while accompanied by a trainer.