Coach Mike Shanahan and the Redskins are poised to absorb the second half of their $36 million salary cap reduction this year (Toni Sandys / The Washington Post)

If the Redskins make another appeal of the salary cap reduction imposed by the NFL, it might be “informal,” a person with knowledge of the case said.

The team seems to have exhausted its formal appeals of the cap cut, the person said, speaking on the condition of anonymity because team officials have not said publicly how they still might contest the penalty. All that might be left, the person said, is an informal appeal to the league to restore some of the lost salary cap space.

“If there’s anything left to come, I would think it might be informal,” the person said.

Several people with knowledge of the case have said they believe it’s highly unlikely that the Redskins will be able to retrieve any of their lost salary cap space.

Redskins officials have said they are not done contesting the case but have not specified how they might challenge the penalty. The team is set to absorb the remaining $18 million of a $36 million penalty imposed before last season.

The league, with the consent of the NFL Players Association, reduced the Redskins’ salary cap last year by $36 million over two years for the way the team structured players’ contracts during the 2010 season, when there was no salary cap. The league ruled that the Redskins and Dallas Cowboys violated no salary cap rules but improperly attempted to gain a competitive advantage. The Cowboys’ salary cap was reduced by $10 million over two years.

The two teams denied wrongdoing and challenged the penalties last year in an arbitration case under the sport’s collective bargaining agreement. The case was dismissed by the arbitrator.

The NFL Players Association filed a collusion complaint last year against the league and teams, accusing them of operating with a secret salary cap in the uncapped year. But U.S. District Court Judge David Doty ruled in December that the union had waived its right to bring such a claim. The union continued to press its case, but Doty ruled again Friday that the claim cannot proceed. Union officials said earlier this week that they already had appealed.