METAIRIE, La. (AP) — New Orleans Saints starting safety Julian Blackmon has a shoulder injury that could sideline him for the rest of the season, coach Kellen Moore said Monday.

Blackmon, acquired by New Orleans after Tyrann Mathieu retired on the eve of training camp, played for the Saints’ entire season opening 20-13 loss to the Arizona Cardinals. He even went home from the Superdome before expressing concern to team medical staff that soreness in his shoulder could be more serious than he initially believed, Moore said.

Blackmon was in on four tackles and broke up a pass during Sunday’s game.

Moore did not immediately say which reserve safety could be promoted to the starting lineup wen the Saints host San Francisco on Sunday. Possibilities include Ugo Amadi, Jonas Sanker and Jordan Howden.