The San Francisco 49ers are dealing with an unexpected injury to safety Malik Mustapha, who underwent ACL repair surgery after suffering a torn graft during Week 18 against the Cardinals. Initially deemed fine, an MRI later revealed the severity of the injury, confirming the surgery by the team. With Mustapha expected to miss the early part of the season, rookie fifth-rounder Marques Sigle may start, as the team has added safeties Richie Grant and Jason Pinnock while losing Talanoa Hufanga to the Broncos.