Losing an elite quarterback can be devastating to a team. No one knows that better than the Arizona Cardinals. They are the poster child for how things can head south in a hurry when the main man goes down.
Since the midpoint of the 2013 season, the Cardinals are 20-4 when Carson Palmer starts, 5-6 without him.
Palmer missed 11 games last season, the last five after tearing an ACL. He was 6-0 as a starter. In those games, Arizona averaged 25.8 points per game. Without him, the Cardinals scored 12.9 per game. They finished 3-4, losing to the Panthers in the playoffs.
''It's demoralizing when you lose your franchise player, the leader of your team,'' Arizona wide receiver Larry Fitzgerald said. ''There's nobody more important than your quarterback on your football team, especially when you have an elite quarterback like we do. It takes a while. It's really frustrating. It demoralizes your team.''
Arizona didn't just lose its starting quarterback. Backup Drew Stanton went down with a knee injury, too. Arizona signed Ryan Lindley from the San Diego practice squad to start the final three contests, all losses.
Coach Bruce Arians believes the team can keep playing at a high level with Stanton. But he said quality backup quarterbacks are ''really hard to find.''
Nobody has to tell Dallas Cowboys fans that. Dallas went 0-7 after Romo broke his left collarbone. They lost the first three with Brandon Weeden at quarterback, then they signed Matt Cassel and lost four more.
When Romo was ready to return, the Cowboys gave up on Weeden. He was released and signed by another team with quarterback injury issues, the Houston Texans.
When the quarterback is hurt, the team's defense feels it.
''If you don't have your starting quarterback naturally a lot of pressure does fall on the defense,'' Arizona safety Tyrann Mathieu said, ''to swing field position, force more turnovers, do everything `extra.'''
Arizona's defense seemed to wear down under that load last year.
''Yeah, it was a lot,'' Mathieu said, ''... Defensively you want to go out there and score touchdowns and make plays and just be an offensive guy. It definitely puts a lot of pressure on a defense, especially as the season goes on and the games get bigger and tougher.''
Teams talk about having a good backup quarterback. But there's a reason they are backups.
''You always want to be able to absorb injuries throughout your football team,'' Cowboys executive vice president Stephen Jones said on his weekly radio show. ''If something happens to this guy, put the next guy in and let's go. The best teams are able to do that.''
Luck was rarely his old self this season amid rumors he was hurt worse than he or the Colts let on. Now he is gone for perhaps five weeks with a lacerated kidney and abdominal muscle injury. So Indianapolis will turn to 40-year-old Matt Hasselbeck, who quarterbacked the Colts in two wins earlier this season.
''I guess I've been doing this long enough you expect the unexpected,'' new Colts offensive coordinator Rob Chudzinski said. ''That's what this job is and that's what coaching is, is a challenge. It's all about challenges. You look at it like it's a jigsaw puzzle. It can come together and it's a matter of getting those pieces and putting it all together, but it can be done. We'll find a way to get it done.''
And in Denver, Manning - one of the best to ever play the position - has been far from his prolific self this season. Now he's been sidelined with a foot injury in favor of untested Brock Osweiler, who has thrown 54 passes in his NFL career.
''To hear coach (Gary) Kubiak say, `Hey Brock, you're going to start this week at Chicago' in front of the whole team, yeah,'' Osweiler said, ''it's a little abnormal.''
AP sports writers Schuyler Dixon in Dallas and Arnie Stapleton in Denver contributed to this report.
AP NFL website: www.pro32.ap.org and AP NFL Twitter feed:www.twitter.com/AP-NFL