Jenkins is in the final year of the contract he signed as a first-round pick out of South Florida in 2008.
He's been extremely inconsistent in his time in Dallas, alternating a Pro Bowl season in 2009 before becoming one of the NFL's lowest-rated CB's in 2010.
In an interview with Calvin Watkins, Jason Garrett said that "the team values Jenkins, but you can't pay everybody, at least right now."
Dallas has sunk a lot of money into the defensive backfield over the last year, with newly acquired free agent CB Brandon Carr receiving nearly $50 million and nickel back Orlando Scandrick, who was drafted the same year as Jenkins, receiving a $27 million extension before last season.
If the Cowboys end up taking a CB in one of the first few rounds of the 2012 Draft, it's likely the end of the road for Jenkins in Dallas, as it wouldn't be feasible to invest a lot of money in four different CB's.