A Romelu Lukaku double, followed by goals from Anthony Martial and Paul Pogba gave the Red Devils their biggest win for three years and the 54-year-old was pleased with the level of performance on show from his side.
The Serbian worldwide was also keen to pay homage to new team-mate Lukaku, who also had an Old Trafford debut to remember, as he took his United goal tally to three goals in two games.
Crespo of course worked with Mourinho at Chelsea and won a title under the manager, and thinks that the United boss will pull it out of the bag in his second season at Old Trafford.
Matic may be thought of a mere destroyer by some, but ask Jose Mourinho and he is "a player with special qualities".
Hamann believes that Matic is a match-winner and questioned why Liverpool did not attempt to sign him by saying, "Matic the missing link to make United title contenders".
"It depends on what is happening or what was happening behind doors and we don't know", he said.
"The only thing I know is that I brought him to Stamford Bridge because I thought he was a player with special qualities and since I left I always thought he could be a flawless player for us". "Thanks to them, I feel very comfortable and I feel like I will be here a long time".
"He likes the team and the team likes him", Mourinho said. It's always oxygen, it's happiness and confidence for them.
"I think we can do better than last season", Mourinho said after his biggest victory as United manager. With two goals in his first competitive game for the club (he did score against Real Madrid in the UEFA Super Cup earlier in the week, but that's a glorified friendly), Lukaku is off to a great start and has already made himself the new darling of the United supporters. He created the first goal by dispossessing West Ham's Pedro Obiang and sparking the break, and proved to be an impenetrable shield in front of United's back four.