However, the Brazilian was then sent off, wiping out the numerical advantage and making for a nervy second half, with Trevoh Chalobah halving the deficit in the 80th minute.
United needed a response after their wimpy derby defeat at Manchester City and they were handed a massive favour by Sanchez, who was shown a red card in the fifth minute after rushing out of his area and clattering into Bryan Mbeumo. United did not take long to take advantage, Fernandes stooping in to head home a cross-shot from Patrick Dorgu as the hosts swarmed around Chelsa's area.
Things got even better for Amorim's side when Cole Palmer was taken off midway through the first half with a suspected recurrence of the groin injury he had just recovered from. It was the third substitute Chelsea boss Enzo Maresca made and surely not even United could blow such an advantage. However, they nearly did.
Casemiro bludgeoned in a second goal with his head before half-time after some aerial bombardment involving Patrick Dorgu and Harry Maguire but then undid all his good work with a stupid sending off right before half-time.
Both his actions to earn deserved yellow cards were totally needless and handed Chelsea the momentum. Chalobah headed home from a corner to send shivers down United's spine but the Red Devils dug deep to preserve their lead and hold on for a vital win.
GOAL rates Man United's players from Old Trafford...
