San Francisco 49ers wide receiver and return man Kyle Williams said Monday he will miss the rest of the season with a torn ligament in his left knee sustained in Sunday's win at New Orleans.

Williams posted on his Twitter account that he has a torn anterior cruciate ligament in the knee. Surgery would be the likely next step.

"Regret to inform y'all I will be out for the season with a torn ACL," Williams tweeted. "Not how I saw things playing out. This is just another obstacle I will have to climb to get back. Looking forward to the challenge!! Love all true fans your prayers are much appreciated."

Coach Jim Harbaugh provided no updates Monday, but did say it appeared Williams was hurt before any contact was made when his foot stuck in the ground.

"We'll see. We haven't got the final report and we'd wait 'til we get that before we brief Kyle and some of the others," Harbaugh said. "It was a hard-hitting game. It took a toll."

Williams and running back Kendall Hunter both were hurt on the same play during the second half of Sunday's 31-21 win over the Saints.

Helped off the field

Both were helped off the field and were soon after taken by cart to the locker room. They were injured on a running play in which Hunter carried the ball for a two-yard gain late in the third quarter.

The 24-year-old Williams — a third-year pro who had two costly fumbles in a 20-17 loss to the Giants in last season's NFC championship game — had 14 catches for 212 yards and a touchdown this year.

With the injuries, Harbaugh is likely to call upon rookie receiver A.J. Jenkins and rookie running back LaMichael James this week against the Rams in St. Louis.

"There's a good chance there'll be some new active guys on Sunday," Harbaugh said. "Yeah, I send that message to some of our young guys, some of our inactive guys that the opportunity is coming. You say that every week to them, 'Be prepared, be prepared.' You'd rather be prepared for your opportunity and have it not come than have your opportunity come and not be prepared.

"To both those youngsters' credit, and others who have been working extremely hard for their opportunity, we feel good and excited that a couple of those youngsters will get that opportunity."