Dallas Cowboys Star Gerald McCoy Suffers Gruesome Leg Injury, Out For Season

Huge blow for the Dallas Cowboys ... star defensive tackle Gerald McCoy just suffered a gnarly quad injury in practice -- and the team now says he's DONE for the 2021 season.

Reporters on scene in Dallas say the defensive lineman -- who just signed a 3-year, $18 MILLION contract with the team this offseason -- went down awkwardly during Monday's workout.

According to multiple witnesses, McCoy was stepped on by a teammate in a routine drill -- and could NOT put weight on the leg as trainers helped the 6-time Pro Bowler to the locker room.

Cowboys exec Stephen Jones confirmed a short time later that McCoy ruptured his right quad tendon -- and will now be headed for season-ending surgery.

32-year-old McCoy was expected to be a key player in the middle of the Cowboys' defense this season ... head coach Mike McCarthy had just praised him earlier this month, saying, "we look for him to be a force inside."