49ers Fear Rookie Mykel Williams Tore ACL in Win Over Giants, Adding to Defensive Injury Woes

The San Francisco 49ers walked away from MetLife Stadium with a 34–24 win over the New York Giants in Week 9, but the result came with devastating news. Rookie defensive lineman Mykel Williams, one of the team’s top draft picks, was carted off the field late in the game after sustaining what appears to be a serious knee injury.

According to Cam Inman of the Bay Area News Group, the 49ers fear Williams suffered a torn ACL during the closing minutes of the contest. The non-contact injury occurred with just four minutes remaining, on the same turf that has drawn criticism in the past for its role in player injuries.

If the early diagnosis proves accurate, Williams would become the latest in a string of key defensive players lost for the season. The 49ers are already without All-Pros Nick Bosa and Fred Warner, both sidelined with long-term injuries. Losing their promising rookie adds another layer of adversity for a team still battling to stay atop the NFC standings.

Despite the string of setbacks, San Francisco’s resilience was on display once again, as head coach Kyle Shanahan’s squad managed to pull off another gritty win. However, the growing list of injuries threatens to test the team’s depth and endurance as the season progresses.

1. Shanahan Praises Rookie’s Growth Amid Heavy Workload

Before the injury, Kyle Shanahan had spoken highly of Mykel Williams’ progress and versatility in his first NFL season. The rookie had been playing significant snaps both inside and outside on the defensive line, stepping up amid injuries to veteran starters. “I think Mykel’s just playing a lot of football,” Shanahan said earlier in the week. “He’s doing stuff outside, he’s doing stuff inside. I’d love for us to take some plays off of him, but with all those guys going down, I think he still ended up getting around 53 defensive snaps last week.” The 49ers head coach also praised the 22-year-old’s durability and competitive spirit. “He’s fighting through some injuries and a lot of playing time,” Shanahan added. “I think he’s growing a lot.” That growth has been apparent on the field. Williams, a standout at Clemson before entering the NFL, has shown flashes of elite pass-rushing ability and improved discipline against the run. His emergence had been a bright spot for San Francisco’s reshuffled defense—a unit that continues to fight through attrition.

2. Defensive Depth Stretched to the Limit

The loss of Mykel Williams compounds an already dire situation for San Francisco’s defense. With Nick Bosa and Fred Warner out for the season, the 49ers have been forced to rotate a patchwork front seven that leans heavily on younger, less experienced players. Defensive coordinator Steve Wilks has had to rely on rotational linemen and practice-squad call-ups to maintain pressure on opposing quarterbacks. The 49ers’ defensive efficiency, once among the league’s best, has dipped in recent weeks as the injuries pile up. Still, the team’s adaptability has been impressive. Backup linemen like Kalia Davis and Robert Beal Jr. have seen expanded roles, while veteran Arik Armstead has been tasked with anchoring a depleted unit. The coaching staff’s challenge now will be maintaining energy and execution over the long haul, especially as the postseason race intensifies. Shanahan acknowledged that sustaining the same defensive intensity without key stars will require creativity and leadership. “We’ve got to find a way,” he said. “Everyone’s dealing with injuries, but we’ve had our share. It’s next man up, and we’ve got guys who can step in and compete.”

3. A Familiar Battle With Adversity

The 49ers’ 2025 campaign has been defined as much by perseverance as performance. Despite losing several cornerstone players, they’ve managed to stay competitive through a combination of offensive balance and defensive grit. Quarterback Brock Purdy and running back Christian McCaffrey have carried the offensive load, while the team’s young defenders have fought to maintain the high standard set in recent seasons. For Williams, the potential ACL tear marks an abrupt pause in what was shaping up to be a promising rookie year. Like many before him, he’ll now face the challenge of recovery and rehabilitation—a test of patience and resilience that can often define a young player’s career. San Francisco, meanwhile, must once again adjust on the fly. The defense that was once the team’s foundation now finds itself in survival mode, forced to rely on depth, discipline, and an unrelenting next-man-up mentality. The 49ers’ ability to overcome injuries has kept them afloat, but each new setback raises the question of how long that can continue. With Mykel Williams likely joining the long list of players on injured reserve, the team’s resolve will be tested yet again.