49ers fear rookie Mykel Williams suffered ACL injury vs. Giants

Head coach Kyle Shanahan offered an early update following the 49ers' 34-24 win over the Giants, expressing concern that Williams may have suffered a significant knee injury.

"We're worried it's an ACL, but you never know until tomorrow," Shanahan told reporters.

Shanahan spoke to Williams after the game.

"He's just down," the coach said. "You never know, so I said, 'Hopefully, it's not the worst, but if it is, hey, that sucks for this year, but that's all that sucks for you. You'll be back next year, and this won't affect you at all."

If confirmed, it would mark another significant blow to a San Francisco defensive line already hit hard by injuries. The 49ers have lost Nick Bosa to a torn ACL, while Bryce Huff remains sidelined with a hamstring issue. Yetur Gross-Matos was placed on injured reserve on Saturday. Losing Williams — one of the team's most promising young defenders — would further test the unit's depth.

"I don't know what the severity of it was, but I was definitely pi--ed," quarterback Mac Jones said. "I was sitting there just getting ready to go back in, and I didn't know who it was. And [then], I was like, 'Oh, Mykel—I hope he's OK.' So just prayed for him, and I know he's walking around and stuff, so hopefully he's doing better."

The 49ers recently traded for Keion White and signed Clelin Ferrell to the practice squad, hoping to bolster the defensive front. Ferrell was elevated for Sunday's game and made an impact with a sack against the Giants.

Despite the growing injury concerns, San Francisco improved to 6-3 on the season with the road win.