As Matt De Lima wrote on here earlier today, it was expected that Arizona Cardinals rookie running back Ryan Williams would miss all of the 2011 season due to what head coach Ken Whisenhunt said was "probably" a torn patellar tendon.
No need for "probably" now; it's been confirmed -- Williams requires season-ending surgery to repair the torn tendon in his knee. According to Kent Somers of The Arizona Republic, Williams will go under the knife at some point early next week. He did not suffer any other damage to the knee.

Fantasy Analysis:

You probably remember that Cadillac Williams tore the patellar tendon in each knee in consecutive years, 2007 and 2008. You can tell that he's obviously not the same player now. There no doubt that this type of injury can have a career-long impact on Williams. However, he's only 21 and should be back at full strength in time for 2012 training camp.
Chris Wells becomes a player who, if nothing else, will get a lot of touches this year. He may still not be very productive with them, but he's going to get a ton of opportunity anyway. I think he moves up from being a probable flex play to a decent RB2, easily among the top 25 running backs. LaRod Stephens-Howling and Alfonso Smith are his current backups, both worth nothing more than a late-round flier.
Also, this is just another reason why you should always hold your fantasy football draft after the last week of preseason games. Hundreds of thousands of leagues have already drafted and now hundreds of thousands of owners have already seen one fairly valuable pick turn into trash before week one. Never hold your draft while preseason games are still being played. There's too much risk that something might happen to one of your players simillar to what happened to Ryan Williams on Friday night.