West Ham had only won one of their previous 19 Premier League matches against United but an early strike from Felipe Anderson and a Victor Lindelof own goal shortly before half-time left the disjointed visitors with a mountain to climb.
When play restarted, Rashford cleverly converted from Luke Shaw's corner but Noble picked out the yawning gap between Chris Smalling and McTominay in the United defence and Arnautovic coolly finished the job 16 minutes from time.
He said: "The third goal killed the team mentally, but he [Scott McTominay] was the best, he had a fantastic attitude, he was aggressive, fearless and courageous".
United's tally of just 10 points from their opening seven fixtures is their joint worst start to a Premier League season, and Ferdinand claimed that the club must decide whether to stick or twist with Mourinho.
The Portuguese boss added: "The third goal killed our mentality because the referee did not see the foul before". "You have to try always and that is my nature as a football professional".
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However, Klopp is a perfectionist and it's this type of preparation that's helped his side do so well so far. It's over 13 years since Chelsea and Liverpool met in the 2005 League Cup final.
At this pace, he likely doesn't make it past Halloween as manager of United.
"As a footballer your DNA is about hard work and effort".
Mourinho also told Pogba this week that he will never captain a United side again, a decision which is reportedly due to concerns over the midfielder's attitude.
It remains to be seen how true the rumours are of United's interest in having Zidane replace Mourinho but there are few candidates more qualified than the French legend and it's hard to pretend that Mourinho's job isn't in jeopardy at this point in time. "There has to be something said".
Arnautovic was in no doubt the Hammers had earned their victory. "I look at my team, whatever the other team is doing is not our stuff".