It proved enough to earn Fulham a point and frustrate a United side who will rue missed opportunities to wrap the game up in the first half.
Blackpool looked to be closing in on the win, but Dembele opened up their defence and former Preston man Etuhu applied a composed finish to earn Fulham a third consecutive draw.
Elsewhere, Manchester United booked its place in the fourth round of the FA Cup and a home tie against Fulham following a narrow 1-0 win over West Ham.
There was still time for Trochowski to pick up a booking that rules him out of the second leg - a further boost to Fulham on a good evening for the west London club.
McDonald has overseen a 2-0 win at Bolton, a 3-0 defeat at Fulham and a goalless draw with Stoke, with Allardyce expected to be at the helm for the home game against Liverpool on Saturday.
The 30-year-old striker was back in the headlines on Monday after he reportedly met Inter Milan's sporting director Marco Branca in a Fulham restaurant to discuss a potential January transfer window move to the San Siro.
West Ham next travel to Blackburn and Fulham before a home game with Everton.
Fulham issued a statement on their official website saying that the dispute between the club and Tigana had not run its course.
Fulham needed a minor miracle to stay up before the match, and manager Roy Hodgson's body language told its own story as events unfolded.
"The right players have certainly been brought to the club, " said Hangeland, who helped Fulham to a club-best seventh in the Premier League last season.
Elsewhere, West Ham drew 2-2 at home to 10-man Fulham in a London derby, rescuing a point with a late goal by youngster Junior Stanislas.
Fulham look a poor side, despite the money spent by Sanchez, and it needed Niemi to be at his best to keep Derby at bay.
Fulham snatched a 1-0 win at cash-strapped Portsmouth thanks to a lucky goal from Bobby Zamora after Clint Dempsey's shot deflected in off the striker's back.
But Fulham suffered a bigger blow in first-half injury time when Koncheskey was sent off for raising his hands to Fagan as they tussled on the flank.
But it was the dismissal of Nevland that had changed the course of the game and, while Fulham had a measure of control beforehand, they were forced into a rearguard action after the dismissal.
It did little to halt the hosts' dominance in the second half, but against the run of play Dempsey provided Fulham with a glimmer of hope, bundling the ball home from Diomansy Kamara's cross.
It leaves Fulham with a huge, but not insurmountable task in west London next week - but their defending will have to improve markedly if their European adventure is to continue into the quarter-finals.
Manager Ian Holloway's newly-promoted Tangerines looked on course for a momentous three points as they came from behind after Bobby Zamora - watched by England coach Fabio Capello - headed Fulham into a first-half lead.
Volz, who had also been terrorised by Malbranque, later saw red for a second booking but Fulham were long a beaten side before Defoe wrapped things up with a fine touch and finish after more good work by Huddlestone.
"Dembele originally joined Fulham as a forward, although his ability to drive forward with the ball and his eye for a pass saw him played in an attacking midfield role last season, a move that proved a huge success, " explained a statement on the club website.
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The game could have turned into a rout had Fulham kept pushing but a series of substitutions slowed the pace and the home side were happy to play out a convincing victory which leaves them in mid-table and leaves West Brom in freefall after five straight defeats.
The draw lifted the Tigers out of the bottom three at the expense of a Newcastle side, who were beaten at home by Fulham, with a point separating the two teams.
And substitute Grishin ended those hopes as he slotted a volley beyond Fulham keeper Mark Schwarzer for a crucial away goal.
Suddenly, every set-piece was a great opportunity for Fulham to take advantage of a West Brom defence which had not previously played together.
That deal was set to be extended before Kallio returned to Craven Cottage because of a Fulham injury crisis.
Fulham were awarded a penalty by referee Jon Moss with four minutes remaining.
Things kicked off Saturday morning with Arsenal traveling to Fulham, a team they had not beaten in their last four matches contested.
The second goal finally arrived via Pratley in the 72nd minute as the in-demand ex-Fulham trainee capped a driving run with an unstoppable shot past Jake Cole.
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