2012 NFL Free Agents: 6 Players Who Won't Be Signed and Will Eventually Retire

NFL careers are short. Many players don't make it to their second contract, but a select few move on to great things and great contracts.

The players on this list have been there. They have all been key contributors to solid teams, but their skills are declining, and they have lost their value.

Every offseason, players with long, successful careers wait in anguish as team after team passes them over.

Here are six free agents who will face that agonizing reality in 2012.

Matt Birk

Anyone who watched the AFC Championship game saw center Matt Birk get whipped consistently by Vince Wilfork.

Birk can still get it done on occasion, but his embarrassment at the hands of Wilfork showed that he is no longer a top talent. His health is declining rapidly, and he will be 36 at the beginning of the season.

With an expiring contract and declining ability, Birk will have trouble finding a team in 2012.

Matt Birk will likely retire before hitting the open market, but if he doesn't, he still might not find any suitors.

Cedric Benson

Cedric Benson seems much older than 29. His talent has eroded swiftly, and his speed has completely disappeared.

Benson doesn't have a lot left to offer an NFL team. He is a marginal power back with no speed or explosion, and he's not known for his veteran leadership, either.

The Cincinnati Bengals will probably be looking for a fresh start at running back, and old, slow running backs simply do not attract attention in free agency.

Sadly, Cedric Benson will probably watching football from home in 2012.

Rashean Mathis

Rashean Mathis has been a good corner for a good amount of time in Jacksonville, but unfortunately, his NFL career looks like it might be over.

Mathis played well in 2011, but he tore his ACL in November. He will be 32 at the beginning of the season, and teams will likely question his ability to recover from such an injury.

If the injury affects his speed in any way, Rashean Mathis will likely be forced to retire due to lack of interest. It would be a sad way to end a solid career.

Donovan McNabb

After delaying the inevitable, the end has finally come for Donovan McNabb.

McNabb has nothing left in the tank anymore. He would be a marginal backup quarterback at best, but he will almost certainly consider himself a starter.

No team in the NFL would consider McNabb a starting-caliber quarterback anymore, as he has had minimal success in the past two years.

After some great years in Philadelphia, McNabb's career will end when he realizes that he will likely never hear from any NFL team again.

Kelly Gregg

Kelly Gregg has long been a successful nose tackle in the NFL, but he is almost certainly wearing down from a decade of physical abuse.

At a position where strength is a must, Gregg's old, weary body will be unable to handle the rigors of an NFL season.

At 35 years old, Gregg must know the end is near. He is one of the most competitive players in the NFL, and he will certainly want another chance. That chance will likely not come.

Terrell Owens

Believe it or not, Terrell Owens never officially retired, so he can still be signed.

It's safe to say, though, that he will not be signed. No team wants to deal with a headcase receiver with his own reality show.

Owens talents did not make up for his ego in the twilight of his career, and no team will want to take on the task of turning a 38-year-old receiver into a team player.

Let's hope Owens will finally bow out gracefully instead of putting himself through another tortuous offseason.