United stormed to the top of the table with its emphatic win, but Mourinho claimed the manner of the victory does not make his side the best team in the country or favorite for the title, the Daily Mirror reported.
“I'm too experienced and stable to lose my discipline, my stability and to think a 4-0 really makes us the best team in the country, the favorites or the dream team,” said Mourinho.
“We're not favorites, we're not the dream team, we're just a team with more confidence than last season, with more time of work together, but I'm calm.
“When I look to the last match, I like many, many things, but the challenge is not to repeat the result, because a 4-0 win is difficult to repeat in the Premier League, but to repeat the same kind of performance.
“We had good tactical discipline in the team, a really good clean sheet, played good football, had a good dynamic in attack, we were scoring goals, winning 1-0 and we kept playing to try to score more goals and to try to play well.
“I liked a lot. I liked the fact the three subs, who are normally disappointed people to be on the bench, even five minutes like Jesse Lingard, 10 like Anthony Martial or 15 like Marouane Fellaini, they performed at same level.
“But this is just the beginning. Last season we played three matches, had nine points and finished sixth.”
United remains in the hunt for Inter Milan winger Ivan Perisic, but Mourinho said he would be happy to go with the squad he currently has if he cannot add a fourth summer signing before the August 31 transfer deadline.
“I don't think we are [in the market] unless something happened that put us in market again,” said Mourinho.
“I'm happy with the squad we have. I am ready to go without a fourth player. If we are out of the market I am fine. I am okay.”
On plans to close the transfer window before the start of next season, Mourinho said, “My opinion is that we have to adapt to the situation, no matter what.
"As a football manager and not a marketing man, just as someone who wants to work with the team and with players, I would prefer the window to close as soon as possible, so everyone knows the players we have, and the deals will be done earlier and nobody will be waiting for the last week and we wouldn't have a situation we sometimes have with players playing game No.1 for one team and game No.2 for another.”
Next for Manchester United is a trip to Liberty Stadium as the Red Devils take on Swansea City on Saturday in their second fixture of the new Premier League season.