Fighting to avoid the sack after a woeful start to the season, Amorim received a welcome boost when Chelsea goalkeeper Robert Sanchez was sent off after just five minutes of Saturday’s clash.
Bruno Fernandes quickly put United ahead with his 100th goal for the club in all competitions in his 200th Premier League appearance.
Casemiro doubled United’s lead before the Brazil midfielder was dismissed for a second booking in first-half stoppage time.
Trevoh Chalobah’s late reply for Chelsea set up a tense finale, but United held on for just their second win in six matches in all competitions this term.
Having kicked off languishing just above the relegation zone, Amorim’s side climbed to ninth place to give the Portuguese coach a little breathing space.
“I felt the urgency. Of course the Sanchez sending off helped us but we had the red card with Casemiro. We like to complicate our game always,” Amorim said.
“It is really important to win because I understand the situation around this club.”
“I have nothing to say to the critics and most of the time they are right. Today we won and it is a good day for us.”
The erratic Sanchez rashly raced out of his penalty area in a bid to clear before Bryan Mbeumo could reach Benjamin Sesko’s flick, but instead sent the United forward crashing to the turf with a reckless challenge.
It was a clear red card for denying a goal-scoring opportunity and there were no complaints from Chelsea about their quickest ever Premier League dismissal.
Filip Jorgensen replaced Sanchez in goal as Maresca took off wingers Estevao Willian and Pedro Neto in a defensive move that immediately backfired.
United went for the jugular and took the lead in the 14th minute when Fernandes, played just onside by Chalobah, timed his run perfectly to meet Patrick Dorgu’s header with a clinical finish from four yards.
Chelsea’s misery mounted when England forward Cole Palmer was forced off with an apparent recurrence of a groin injury, making it a remarkable three substitutions in only 21 minutes for the Blues.
For once, the luck was all going Amorim’s way and Chelsea imploded to gift United their second goal in the 37th minute.
Jorgensen stood rooted to the spot as Reece James’s sliced clearance was headed on by Harry Maguire to Casemiro, who nodded home from close range for his first league goal in 11 months.
United struggled to find any rhythm in the second half and Chalobah reduced the deficit in the 80th minute when he rose unmarked to meet James’s cross with a powerful header that flashed past Altay Bayindir from 12 yards.
It was too late to stop Chelsea slumping to their first league defeat this season as Amorim breathed a sigh of relief. (AFP)
