Blaine Gabbert and Starting QBs on Shaky Ground

In the National Football League, quarterback can be the most important position on the playing field, and having an elite signal-caller such as Aaron Rodgers can be a big step toward propelling an NFL team toward postseason glory.

However, some NFL clubs aren't so lucky. Whether it's due to poor play, another quarterback nipping at their proverbial heels or a combination of the two, the following NFL quarterbacks enter the 2012 season with a grip on the starting job that isn't exactly ironclad.

Blaine Gabbert, Jacksonville Jaguars

It didn't take long for the Jacksonville Jaguars to throw rookie quarterback Blaine Gabbert into the fire last year, as by the third game of the 2011 season, the former Missouri star was starting under center.

That move may have backfired, however, as Gabbert struggled mightily in his inaugural season.

Gabbert managed only 5.4 yards per attempt and struggled mightily with reading NFL coverages, completing barely over half of his passes.

Jaguars head coach Mike Mularkey recently reiterated that Blaine Gabbert "is our starting quarterback," but that may not stay that way for long if Gabbert keeps posting quarterback ratings in the 60s.

Kevin Kolb, Arizona Cardinals

The Arizona Cardinals were filled with optimism when they acquired quarterback Kevin Kolb from the Philadelphia Eagles last year for a second-round pick and cornerback Dominique Rodgers-Cromartie, with Arizona general manager Rod Graves raving about Kolb's upside at the time to ESPN:

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We saw a quarterback there that we felt very excited about, we feel like he can come in and get the job done for us and put us in a position to be a championship-caliber football team.

"

Graves may be reconsidering that assessment after inking Kolb to a $65 million contract, only to see Kolb suffer through an injury-marred season that saw the sixth-year veteran miss seven games.

The pressure is going to be big on Kolb to start earning that money this season, and a slow start is sure to lead to calls for a change under center in the desert.

Matt Cassel, Kansas City Chiefs

Much like Kevin Kolb, quarterback Matt Cassel of the Kansas City Chiefs was a career backup who parlayed some on-field success into a fat contract with another team.

And much like Kolb, Cassel has struggled at times to earn that cheddar since taking over as a starter.

Cassel played well in 2010 but slogged through a miserable 2011 season, missing seven games due to injury and throwing only 10 touchdown passes in the nine games in which he did play.

Kansas City general manager Scott Pioli recently told Sports Illustrated that "We like Matt Cassel, and we think Matt Cassel is a good quarterback," but if the team's pursuit of Peyton Manning in the offseason is any indication, their patience may be wearing thin with the eighth-year veteran.

Mark Sanchez, New York Jets

The New York Jets struggled through an up-and-down 8-8 2011 campaign filled with controversy and distractions.

However, quarterback Mark Sanchez actually had the best statistical season of his career, setting career highs in touchdown passes and yardage.

The Jets can proclaim Sanchez the unquestioned starter until they're blue in the face, but the simple fact is that the very presence of the newly acquired Tim Tebow in the Big Apple brings with it a quarterback controversy.

All it will take is a few ill-conceived early season interceptions, and Gang Green's supporters are going to start clamoring for Sanchez to get the hook.

Matt Hasselbeck, Tennessee Titans

Veteran quarterback Matt Hasselbeck experienced something of a career resurgence last year, as the 36-year-old posted the most passing yards and touchdowns and highest passer rating that he's tallied since the 2007 campaign.

However, the 14th-year pro threw only four touchdowns against seven interceptions from Week 11 on last year.

Reporters such as ESPN's Paul Kuharsky believe that Hasselbeck will be the Week 1 starter in Nashville, stating that "unless he’s horrible in July and August, I can’t see how he gets demoted from the starting job."

On the other hand, youngster Jake Locker is going to be nipping at Hasselbeck's heels all season long, and if the Titans struggle out of the gate, it may be time for a changing of the guard at the quarterback position.