United's destiny in their bid for top-flight safety was placed back in their own hands on Saturday afternoon after relegation rivals Burnley slipped to a 3-1 defeat at home to Aston Villa.
That result left Leeds level on points with the Clarets and still with a far worse goal difference but having played one game less.
Leeds headed for Sunday's clash at Arsenal sat fourth-bottom in the division and two points ahead of third-bottom Everton but with the Toffees having a game in hand.
But the picture dramatically changed following a calamitous first-half for Leeds at Arsenal as Luke Ayling was shown a straight red-card shortly after a brace from Gunners striker Eddie Nketiah.
The Gunners forward was gifted his first goal via a huge clanger from Whites 'keeper Illan Meslier and Ayling's season is now over as the defender will be suspended for the next three games.
Leeds pulled a goal back through Diego Llorente after the break but the damage was done and Jesse Marsch's side fell to a 2-1 defeat, the effects of the reverse were then compounded by Everton winning 2-1 at Leicester City.
That success allowed the Toffees to climb out of the relegation zone and up 16th place, Burnley dropping to 17th and Leeds sliding into the drop zone ahead of bottom two Watford and Norwich City who have already been confirmed as down.
Leeds stay level on points with Burnley and both sides have three games left but United's goal difference is minus 35 whereas Burnley's is minus 17.
United are now one point behind Everton who also have an extra game in hand.
Sunday's action saw a huge change in the betting for Premier League relegation and here is the very latest predicted finishing positions and survival prospects of each side based on the latest odds to go down.