The most important position in the NFL is often the most vulnerable.

Just look at the Dallas Cowboys, who have imploded since quarterback Tony Romo went down with a broken collarbone in Week 2.

By the time Romo returns, it might be too late for the Cowboys.

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That said, Dallas is hardly the only team to skimp on a backup quarterback and wind up paying a heavy price. Much rarer are teams such as Pittsburgh, which wisely had both Michael Vick and Landry Jones waiting in reserve when Ben Roethlisberger was injured early in the season. They kept the Steelers afloat, going 2-2 while Big Ben was out.

The Cowboys haven't won since Romo was injured in a victory over at Philadelphia nearly seven weeks ago.

Not surprisingly, his mere return to practice this week was quite a morale booster.

''When you've got a guy like that, it's just great to see him on the field,'' tight end Jason Witten said. ''I think we're all excited to get him back out there.''

When Romo was injured, the Cowboys first turned to Brandon Weeden, who ran his career record as a starter to 5-19 with three straight defeats. Next up was Matt Cassel, who keeps landing jobs despite a largely mediocre resume. He's run the losing streak to five straight heading into Sunday's game against the Eagles.

If Romo makes his expected return in Week 11, he'll likely need to pull off one of his greatest comebacks to salvage a playoff berth - even in the lowly NFC East.

It's easy to understand how teams get themselves in this sort of QB predicament.

When all goes according to plan, the backup never sees the light of day on a team with a franchise quarterback, such as New England's Tom Brady or Green Bay's Aaron Rodgers.

The chances of a devastating injury have certainly been reduced by the league's ever-vigilant rules to protect its most valuable commodities. When also dealing the demands of the salary cap and 53-man roster, the natural tendency is to save money by going with a low-paid guy behind the team's biggest star.

Here's a look at which of the league's top teams would be hurt the most by a major injury at QB:

- GREEN BAY (6-1). The Packers are doomed if Rodgers goes down. The backup is someone named Scott Tolzien, who might as well be in the witness protection program. Undrafted out of college, he was waived by both San Diego and San Francisco before catching on with the Packers. He's played four games in five years, with one touchdown and five interceptions. The Packers also have rookie Brett Hundley, a fifth-round pick out of UCLA. Not good.

- ATLANTA (6-2). The Falcons are blessed to have one of the league's most durable quarterbacks. Matt Ryan has missed only two games in his career, both in 2009. Chances are, you have no idea who is backup is. You're certainly not alone. Even die-hard Falcons fans would have a hard time picking out Sean Renfree, a seventh-round pick from Duke who's been holding a clipboard in Atlanta for the last three years. His next pass will be his first in the NFL.

- CINCINNATI (8-0). AJ McCarron was a great college quarterback at Alabama. The NFL is another story. The unbeaten Bengals go to bed every night hoping nothing happens to starter Andy Dalton. Otherwise, their dream season goes down in flames.

- DENVER (7-0). For those who think Peyton Manning is all washed up, just imagine the Broncos with Brock Osweiler at quarterback. It's hard to see them unbeaten, that's for sure. Osweiler might be the quarterback of the future, but it's best to stick with Manning as long as possible.

- CAROLINA (7-0). Given his propensity for running, Cam Newton is probably at greater risk for injury than most quarterbacks. Therefore, the Panthers should be better prepared at No. 2. Derek Anderson has experience, but that's about it. Outside of an improbable Pro Bowl year with Cleveland in 2007, his record as a starter is 10-20.

Unbeaten New England, the defending Super Bowl champion, would certainly be in a bit of trouble if Brady was sidelined.

But let's not forget that Brady went from unknown backup to certain Hall of Famer, while Cassel is still riding the memory of one glorious season filling in while Brady was hurt. We can only assume second-year quarterback Jimmy Garoppolo would be an All-Pro should he ever get a chance to play.

For one team, it doesn't seem to matter who's backing up.

For everyone else, it might be worth paying a bit more attention to that overlooked position.

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Paul Newberry is a national writer for The Associated Press. Write to him at pnewberry(at)ap.org or on Twitter at

www.twitter.com/pnewberry1963