Harlequins scored four tries against Sale in the affected match
Sale have been deducted one league point and fined £5,000 for fielding an unregistered player in their Guinness Premiership game against Harlequins.
The penalty was given out for including hooker David Ward in the squad for the 38-20 defeat at The Stoop on 22 March.
"We are considering what actions may be taken," said Sale chief James Jennings.
Sale need to record a bonus-point win over Northampton in their final league game on Saturday and hope other results go their way to earn a play-off spot.
Jennings added: "The club are very disappointed that an administration failure has resulted in this sanction."
The point deduction leaves Sale five points adrift of the play-off places, but it has been their form in recent weeks that has really cost them.
Friday's 28-6 bonus-point victory over Harlequins was only their second win in seven Premiership games.
Bath and London Irish currently occupy third and fourth place and if either lose, it will open the door for Sale should they beat Northampton and earn a bonus point at Edgely Park on Saturday.
Bath are home to ninth-placed Saracens while the Exiles travel to second-bottom Worcester.
But the Sharks could be left to rue the decision to bring Ward on as a front-row replacement in the 72nd minute of the game, when they were trailing Harlequins 31-15.
He had been de-registered by the Sharks' academy manager on 27 January and this information was not communicated within the the club.
Jennings did not dispute the breach at a disciplinary meeting with a joint Rugby Football Union and Premier Rugby Limited panel.
Four other cases of teams fielding ineligible players were noted by the panel in reaching their judgement.
Leicester in 2003 and 2007, Saracens in 2003 and Bristol in 2007 were all deducted one point for similar offences.