The Washington Redskins and the Minnesota Vikings continue to work on a tentative trade involving Redskins quarterback Donovan McNabb, a source confirmed late Tuesday.

The deal, if it can be completed, would be contingent on McNabb restructuring his contract, the source said. It could force McNabb, who could make up to $14.75 million in 2011 if the Redskins keep him, to take a one-year deal for less than half of that.

The problem for McNabb is that he may not have much time to make a decision, the source said, because the Vikings are evaluating the veteran quarterback market.

The Vikings' quarterback situation is unsettled with the retirement of Brett Favre and free-agent backup Tarvaris Jackson has agreed to a deal with the Seattle Seahawks, sources confirmed to ESPN.com. Minnesota drafted quarterback Christian Ponder with the 12th overall pick in the 2011 draft and unproven Joe Webb also is on the roster.

The Redskins gave up two draft picks last offseason to the Philadelphia Eagles for McNabb, but the quarterback's lone season with Washington was troublesome. He was benched twice in a 6-10 season, and there were testy exchanges involving his agent, Fletcher Smith, and the team.

Despite his struggles, the Redskins gave McNabb, who will turn 35 in November, a five-year contract extension nominally worth $78 million -- but the only thing it guaranteed was that the quarterback would receive an extra $3.5 million last season. The deal contains a clause that allows the Redskins to cut McNabb before this upcoming season with no further financial obligation.

Eagles fans in New York at the 1999 draft booed vociferously when the team selected McNabb instead of Texas running back Ricky Williams with the No. 2 overall pick.