We're at the official halfway point of the NFL season and already 11 teams have had to change quarterbacks because of injuries or ineffectiveness.

Rarely does a quarterback change produce success, especially in the NFL, where stability at the position might be the most important factor in a club's long-term success. No other position in sports is more directly meaningful to a team's bottom line.

Just look at the first half of this NFL season. So far, teams are 5-17 in games in which their backup quarterbacks have started. And two of those wins were recorded by Brian Hoyer in Cleveland after Browns coach Rob Chudzinski benched original starter Brandon Weeden. The 3-4 Browns will start Jason Campbell, their third starter, this week against the Kansas City Chiefs. The 1-5 Vikings have already gone through Christian Ponder, Matt Cassell and Josh Freeman. Predictably, the winless Buccaneers and Jaguars have unstable quarterback situations.

None of this bodes well for Chicago and St. Louis, both of which will start backups this week in the wake of injuries to Jay Cutler and Sam Bradford.

Buffalo Bills coach Doug Marrone can sympathize. He thought he'd solved the club's longstanding issues at the position when he selected Florida State's E.J. Manuel in the first round of the NFL draft in April. Then Manuel hurt his knee in Week 5 and Marrone has been forced to start inexperienced Thad Lewis the past two weeks and sign former LSU standout Matt Flynn as insurance.

"It's important, especially to change at that position," Marrone said. "It's more important than any other one to have someone that can go out there day in and day out, practice every day and work together and stay is very important to that position. ...

"The league is driven by that position. There's a lot of good players, but you have to be right about that one, there's no doubt about it."

After years of quarterback shuffling, the Saints have enjoyed unprecedented stability at the game's most important position thanks to Drew Brees' remarkable durability.

Brees has started 117 of 118 games since he joined the Saints in 2006. The only game he missed was the meaningless 2009 season finale against Carolina when the Saints rested their starters. He sat out the San Diego Chargers' 2004 season finale for similar reasons or he'd be riding an amazing 153-game starting streak (also factoring in final three games in 2003), which would be the longest in the NFL.

The last time Brees missed a start because of injury or otherwise was Dec. 7, 2003, when he was benched for a five-game stretch by Chargers coach Marty Schottenheimer in favor of Doug Flutie.

The streak is a source of immense pride for Brees, and rightfully so. He understands his importance to his team's success. He's played through injuries that would have sidelined other quarterbacks, most notably a sprained knee in 2010.

"Some of that's luck," Brees said this week. "Some of that's just certain elements of being healthy that are out of your control, as far as what happens game day in the pocket.