The Miami Herald reported Long was protecting on a quick pass when he fell to the ground in a heap of other players. Long remained on the turf for at least two minutes.
Long was helped to his feet and was seated on a cart parked on the sideline of the Dolphins' indoor practice bubble. Trainers studied the area between his knee and ankle. The Herald said Long "shook his head in disgust" as he was tended to.
Coach Joe Philbin did not provide an update on Long's status during his post-practice news conference.
Long, 27, is regarded as one of the best left tackles in football. The No. 1 overall pick in the 2008 draft, Long has been named to the Pro Bowl in all four of his seasons in Miami.
Long dealt with knee and biceps injuries last season that forced him to miss a pair of regular-season games, the first two absences of his career. He has been portrayed as a vocal and respected team leader on the current season of HBO's "Hard Knocks."