The 49ers knew the 2025 NFL Draft would be a hugely important one for the future of their team and particularly their defense. San Francisco focused heavily on that side of the ball last year, spending each of the franchise’s first five picks on defense and using six selections in total on that unit. Though the overall performance of a defense ravaged by injuries can be considered underwhelming, several of those draft picks provided reason for optimism.
Defensive tackles Alfred Collins and CJ West
had a clear positive impact on the run defense, with their growth evident as the season progressed. Like that duo, cornerback Upton Stout displayed hugely impressive flashes down the stretch and arguably emerged as the pick of the 49ers’ rookies by complementing his ultra-aggressive play in run defense with some standout moments in pass coverage.
While he came out of the lineup after starting the first seven games, Marques Sigle’s performance in the playoff win over the Philadelphia Eagles lent credence to the notion of him being a long-term contributor.
Yet the most significant pick the 49ers made in the 2025 draft was that of Mykel Williams 11th overall. Save for third-round linebacker Nick Martin, who played only 15 defensive snaps, it is Williams who is perhaps the toughest defensive rookie to assess, his season having been ended by a torn ACL in Week 9.
The frustration is that Williams was beginning to provide consistent evidence of why the 49ers selected him with their highest draft pick since 2021. The hope will be that the length of time he will spend rehabbing the injury does not hinder his hopes of a year-two leap.
Williams was drafted primarily for his influence on run defense, and in the belief that the 49ers will be able to extract upside from him as a pass rusher.
The jury is still out regarding his pass-rushing abilities. Williams had only one sack in nine games as a rookie, but he still produced plenty to suggest he can blossom into a force in that area of the game.
He was triple-teamed in Week 1 on the decisive play in the season-opening win over the Seattle Seahawks, clearing the way for Nick Bosa to force a fumble from Sam Darnold. Williams collapsed the pocket from the interior — which is where the 49ers view his future as a pass rusher — on another Bosa sack against the New Orleans Saints and had a season-high six pressures in the Week 3 win over the Arizona Cardinals. Williams was enjoying another strong game against the New York Giants when he went down.
But there can be no doubt as to Williams’ impact on the run game.
The 49ers’ run defense ranked sixth in EPA per play Weeks 1-9 with him on the field. Across the remainder of the regular season, it ranked 26th.
That disparity is no coincidence. Williams did an excellent job of setting the edge in the run game, showing the ability to dominate against tight ends and hold his ground against offensive tackles.
While Williams only had four tackles for loss, his success as a run defender is better illustrated by the fact his average depth of tackle against the run was minus 0.1 yards. Per Pro Football Focus, that was the best average of any edge defender with at least 100 run defense snaps.
Simply put, Williams was not being moved off the ball and, though his season was cut short, he still displayed an impressive propensity for making run stops. Indeed, his run stop rate of 6.2% was the third-best among the 11 rookie edge defenders to play 100 snaps against the run.
Far too often in recent years, the 49ers have been bullied at the line of scrimmage when defending the run, and that was a common occurrence when Williams’ season was brought to a premature end. The 49ers have a lot of decisions to make on the personnel front this offseason, but, as his numbers indicate, few things are as important this year as Williams being healthy in time for the Niners to become the bullies in 2026.
