It was pretty clear to anyone who saw it that Carson Palmer's knee injury was a serious one. Guys don't usually crumple to the ground without getting touched and grab their knee unless something very bad has happened. There's no official diagnosis yet, but the word from sources within the organization is that Palmer tore his ACL. (Update: it's official)

This is a deeply shitty turn of events for both Palmer and a Cardinals team that sports the best record in football. Palmer has already missed three games this year, including the team's only loss, but in the games he has started, the 34-year-old has been solid. Palmer's 2013 was a little rough, but this year he's been exactly what the Cardinals hoped they were getting when they plucked him out of Oakland after the 2012 season: a steady, veteran quarterback who can protect the ball and also fling it deep every now and then.

The Cardinals were so pleased with Palmer's performance that they signed him to a three-year, $50 million extension on Friday. Unfortunately for Palmer, the deal is only guaranteed through 2015, for $20.5 million. Depending on just how bad this injury is, Palmer may end up not even playing another game for the Cardinals. If he has to miss all next season rehabbing, the Cardinals are much more likely to cut him loose and eat the $20.5 million than go charging into 2016 with a 35-year-old quarterback who hasn't played in a year.

For now, the Cardinals have to convince themselves that they can be a Super Bowl contender with Drew Stanton running the offense. That's about the saddest position an 8-1 football team can find itself in, but that's what happens when you break one of the NFL's most sacred rules: don't ever sign Carson Palmer to a big extension.