Next Man Up: How Malik Mustapha and 49ers' Deep Secondary Saved the Day in Week 4

The San Francisco 49ers improved to 4-0 on the 2026 season following a 24-14 victory over the Denver Broncos. While defensive coordinator Raheem Morris was forced to adjust on the fly due to mid-game injuries in the secondary, Pro Football Focus (PFF) released its defensive grades, highlighting elite safety play and interior pass-rush production despite a tough afternoon for a few key starters.

Free safety Malik Mustapha turned in the highest defensive evaluation of the afternoon. Logging 21 defensive snaps across multiple stretches, Mustapha earned an 81.5 overall defensive grade. His impact was felt most in coverage, where he earned a team-high 73.7 grade across 15 coverage snaps without allowing a single reception and recording a pass breakup.

Starting safety Ji'Ayir Brown anchored the deep third over 66 snaps, posting a 69.9 overall grade and a 70.1 coverage grade after yielding just two catches for eight yards. Up front, defensive tackle Sebastian Valdez stepped up in limited work, earning a 68.7 grade on 25 snaps, while linebacker Dre Greenlaw posted a 68.3 overall mark on 58 snaps against his former team. Rookie cornerback Renardo Green rounded out the top five with a solid 65.4 grade on 67 snaps.

Injuries and heavy target volume created difficult matchups for several contributors down the depth chart. Cornerback Upton Stout logged the team's lowest defensive mark (38.8) on 37 snaps before exiting with a shoulder injury. Targeted eight times on the afternoon, Stout allowed eight completions for 80 yards, resulting in a 35.5 coverage grade.

Defensive tackle Naquan Jones (42.6) and defensive end Keion White (48.1) struggled to generate high run-defense marks, while linebacker Jaden Dugger (49.4) and defensive tackle Gracen Halton (49.8) also registered sub-50 overall grades.

While San Francisco's defense did not record a sack on Bo Nix, the unit accumulated 16 total pressures across seven different defenders.

Defensive tackle Osa Odighizuwa registered a game-high 75.5 pass-rush grade, generating two pressures and two tackles. Linebacker Dre Greenlaw led the team with four pressures, while Keion White added three. Romello Height, Ogbo Okoronkwo, and Sebastian Valdez joined Odighizuwa with two pressures each, and Mustapha logged a pressure on a blitz scheme. Defensive end Matthew Judon struggled to make an impact, receiving a game-low 50.1 pass-rush grade with zero pressures on 15 snaps.

In the run game, safety Marques Sigle earned a team-best 73.6 run-defense grade alongside a game-high 84.6 tackling grade (six tackles, zero misses). Conversely, Odighizuwa received the game's lowest run-defense grade at 31.8.

All-Pro linebacker Fred Warner endured an unusually quiet afternoon by his standards, posting season-low marks across the board. Warner recorded a 57.4 overall defensive grade, impacted by a 52.5 coverage mark and a 35.1 tackling grade after being credited with two missed tackles.

Overall, San Francisco defenders logged nine missed tackles on the afternoon, with Greenlaw, Stout, and Warner missing two apiece.

Raheem Morris' defense continues to display bending-not-breaking resilience. Despite missing key pass rushers and shuffling secondary personnel mid-game, the defense held Denver to 14 points and secured the key stops needed to preserve San Francisco's unbeaten record.