Gamecocks coach Steve Spurrier said Wednesday that Stadnik, a 6-foot-5, 285-pound junior from Greensboro, North Carolina, hadn't recovered as well as hoped after surgery on his right shoulder.
Coming into summer camp, Stadnik was listed as the backup right guard behind senior starter Will Sport.
Stadnik missed summer camp in 2014 with a knee injury and played only five games last year.
Stadnik's twin brother, Clayton, made five starts at center in 2014. However, he lost 40 pounds after having his tonsils removed and switched to tight end.