Haskell flattened Jamie Roberts with a shoulder-high challenge in the 76th minute that was also late, receiving a straight red card from referee Roman Poite and ending the groggy Wales centre’s afternoon.
The England flanker faces a suspension that could affect his availability for the NatWest 6 Nations, but his more immediate concern will be Wasps’ implosion at Twickenham Stoop.
Leading 21-0 after 30 minutes, they leaked a succession of tries, grabbed the bonus point, before falling apart once again as touch downs from Danny Care, Elia Elia and James Chisholm completed a remarkable fightback by Quins.
Harlequins’ interest in Europe was extinguished long ago – they had lost all four previous matches of this season’s group phase – but a team weakened by injury and suspension fought to the end and were rewarded.
It was the 80th minute when man of the match Chisholm picked and drove over from close range as shell-shocked Wasps rubbed their eyes in disbelief at having thrown the game away.
Mathematically they can still qualify for the knock-out phase, but they face mission impossible against pool leaders Ulster at the Ricoh Arena next weekend to progress.
An uneventful first quarter came alive in the 17th minute when Wasps attacked from a line-out and were rewarded by crossing several phases later.
Haskell could now miss the start of the Six Nations (Getty)
Both tries had been scored with Quins prop Lewis Boyce in the sin-bin…