West Ham hammered Blackpool to return to the top of the Championship despite having to play for 35 minutes with midfielder Henri Lansbury in goal.
Substitute Lansbury was forced to don the gloves after Robert Green was dismissed for a foul on Roman Bednar.
At that stage United led 2-1, with James Tomkins and Nicky Maynard scoring for the visitors before Kevin Phillips pulled a goal back for Blackpool.
United sealed a great win with goals from Gary O'Neill and Ricardo Vaz Te.
It is a real testimony to West Ham's promotion credentials that despite their numerical and personnel disadvantage they were still able to comfortably overcome a Blackpool side that had gone seven matches unbeaten before this game.
Ian Holloway's side looked a shadow of the side of recent weeks, but this should take nothing away from the Hammers.
Prior to what could, and probably should have been a game-changing red card incident in the 53rd minute, Sam Allardyce's men had dominated.
They seized control of the match during a four-minute spell in the first half, during which Tomkins headed home Mark Noble's free-kick and Maynard converted Joey O'Brien's cut-back for his first West Ham goal since joining in January.
Desperate for a foothold in the game, Holloway sent on Kevin Phillips and the veteran striker gave his side just that in first-half injury time, nodding home Alex Baptiste's speculative cross.
The contest was seemingly thrown wide open eight minutes after the break when Green was sent off after chasing rashly from his line to bring down the onrushing Bednar.
However, West Ham - who had not named a goalkeeper among their substitutes - were largely untroubled after that as emergency goalkeeper Lansbury was shielded superbly by his defence.
The visitors gave themselves breathing space with just over 15 minutes to go when O'Neill lashed a crisp 20-yard drive into the bottom corner after Winston Reid's effort from Vaz Te's corner was blocked by Stephen Crainey.
Phillips rattled the inside of the post with a lofted volley for the home side before Vaz Te put the result beyond all doubt when he raced clear to open his own Hammers account with a neat finish.
Blackpool manager Ian Holloway:
"It was pretty horrendous from our point of view. Only one team turned up. In every single way they were better than us.
"They were more professional than us, they played it in the right way on a difficult surface and we just made mistake after mistake after mistake.
"Just about everything that could go wrong did. I felt my lot were caught in the emotion of it. They were not professional, they did not get it right and we were beaten by a better team."
West Ham manager Sam Allardyce told BBC Radio 5 live:
"The outstanding quality from my players was there in abundance. That was a remarkable achievement, a remarkable performance and a remarkable result.
"From the very, very start we controlled the game. We have come out with a huge amount of credit with our display.
"Three games on the trot we've now been reduced to 10 men and we've won two and drawn one. It is the unfortunate ruling by the bosses at the league, which I thought was outrageous at the time, to reduce the substitutes from seven to five.
"That ridiculous decision has caused a lot of us managers to not put a goalkeeper on the bench. We took the gamble and it paid off because Henri Lansbury was outstanding in goal."