Manchester United held off a second-half fight back from Chelsea to win 2-1 after both teams were reduced to 10 men in the first half amid torrential rain at Old Trafford.
Chelsea goalkeeper Robert Sánchez was sent off after just five minutes when shown a straight red card for bringing down Bryan Mbeumo when the United forward was running through on goal.
Chelsea coach Enzo Maresca responded by making a double substitution, with backup keeper Filip Jorgensen replacing Estêvão and defender Tosin Adarabioyo coming on for another forward, Pedro Neto.
He made a third change in the 21st when Andrey Santos had to replace Cole Palmer, who appeared to injure his left thigh.
By then United had made the most of its numerical advantage with Bruno Fernandes scoring in the 14th.
Casemiro made it 2-0 with a header in the 37th but the Brazil international was sent off for a second yellow card in the fifth minute of first half added time for a foul on Santos.
Trevoh Chalobah pulled a goal back for Chelsea in the 80th minute to prompt a nervy finale. But Man United held on for just their second win of the season and some much-needed respite for under-pressure manager Ruben Amorim.
Information from The Associated Press was used in this report.
