From Mike Chappell's piece:
Pro Bowl tight end Dallas Clark was unable to finish the workout after injuring his left leg while running a pass route. There was no immediate comment on the severity of the injury.
After stutter-stepping his feet to stay inbounds near the back of the end zone, Clark pulled up lame. He walked slowly toward a sideline, flexing his left leg before being met by a trainer.
Clark was taken to a treatment tent near the practice field, finally emerging with a wrap around his upper left leg. He didn't return to practice and left a few minutes early on a cart.