Mustapha logged 76 combined tackles (44 solo) and defended three passes (including one interception) across 12 regular-season starts in 2025.
Mustapha opened the regular season on the PUP list after undergoing successful surgery on the knee he injured at the tail end of the 2024 campaign. The sophomore safety missed only one game past the minimum four-week requirement and looked as dominant as he did prior to tearing his ACL. Mustapha reclaimed his starting strong safety job in Week 6 and still surpassed last year's tackle total (72) despite appearing in four fewer games. Following the 49ers' playoff run, the 23-year-old will attempt to combine good health with continued strong play while starting alongside Ji'Ayir Brown in 2026.