As the rain poured over Old Trafford, Chelsea’s prospects were heavily dampened just five minutes into proceedings when Robert Sanchez rushed out of his goal and brought down Bryan Mbeumo after being beaten to Benjamin Sesko’s flick-on.
Enzo Maresca responded with a double change, but the pressure from the Red Devils was unrelenting and the shaken Blues went behind after 14 minutes, with Fernandes just about staying onside and turning Patrick Dorgu’s header past Filip Jorgensen for his 100th United goal.
Maresca continued to desperately fish for answers as he brought Cole Palmer off for Andrey Santos in the 21st minute.
However, just as it was starting to look as though those changes had helped Chelsea limit the damage caused in a torrid first half, the visitors failed to deal with the cross from a short corner routine and Luke Shaw kept the ball alive for Casemiro to head it home and compound their misery.
United were enjoying themselves so much that the nine minutes of added time were met with cheers, but Casemiro received a second yellow for fouling Santos in the fifth of those having needlessly been booked for a challenge on Enzo Fernandez in the 17th minute.
Ruben Amorim reacted by bringing Sesko off for Manuel Ugarte ahead of a gritty start to the second half, with conditions adding some extra difficulty as water splashed up off the pitch.
Chelsea still tried to make things happen and momentarily thought they had a lifeline after the hour mark when Tosin Adarabioyo flicked Reece James’ corner towards Wesley Fofana, who was offside before heading the ball in.
The visitors eventually gained renewed hope with 10 minutes left, as James floated in a cross that Trevoh Chalobah rose unchallenged to head past Altay Bayindir.
Despite that goal making nerves set in across Old Trafford and Fernandes seeing his strike tipped wide, Ugarte blocked Santos’ late attempt as United saw out seven minutes of added time to secure a second win from their last three matches and offer Amorim some relief.
They also inflicted Chelsea’s first PL defeat of the season, while also leaving the Blues winless in their last three across all competitions.
Flashscore Man of the Match: Matthijs de Ligt (Manchester United)
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