Gardner, a seventh-round pick, needs left shoulder surgery that will ultimately land the defensive end on injured reserve. He suffered the injury on July 26 but returned for some work on Aug. 3 only to realize there was not enough strength for him to continue playing. His senior season at Stanford was ended early because of a torn pectoral muscle.
Gardner confirmed the news via social media.
He is the second Cowboys draft pick to need surgery. Second-round defensive end DeMarcus Lawrence had a broken foot repaired and could miss the first three to six regular-season games. The Cowboys were hoping Gardner could be part of the defensive line rotation.
If the Cowboys place Gardner on injured reserve now he would be subject to waivers and could be claimed by another team. If they wait to the first cut-down date on Aug. 26, they can move him straight to injured reserve.