The scoreline matched their opening-day destruction of West Ham United after Romelu Lukaku, Paul Pogba and substitute Anthony Martial scored between the 80th and 84th minutes to add to Eric Bailly's first-half opener, his first goal for the club.
Jose Mourinho has praised Anthony Martial's impact as a goal-scoring super-sub against Swansea at the weekend, the Manchester United forward having now scored in both league games of the season.
Now, these victories were against West Ham and the Swans, so we should be cautious before crowning them after two weeks, and everyone is eager to see how United will do against stiff competition.More news: China Unicom surges to two-year high on restructuring
Mourinho and his men will look to continue their unbeaten start when they welcome Leicester City to Old Trafford on Saturday afternoon.
Henrik Mkhitaryan, who was named the man of the match with two assists late on, believes United are now getting some more luck after they drew plenty of games they should have won last season. "In certain games, Mourinho has to let full-backs bomb on, and they had so many options".
"I would say he is probably the best midfield player in the world".
"I made some offensive changes because I don't want to be a coach happy to lose 1-0 at home, but we ended up playing to their strengths and they punished us".
This time past year Mkhitaryan was struggling to get games with Manchester United after moving from Borussia Dortmund.More news: Victoria Beckham Tears Up Sending Son Brooklyn to College
France worldwide Martial, 21, scored 17 goals in all competitions following his 2015 move from Monaco, but found the net only four times in 18 league starts last season.
"I think the supporters felt that way too".
"But we had pressure and we were doing what we had to do and we scored from a set-piece".
Manager Jose Mourinho told BBC Sport despite taking a while for his team to make an impact he was relaxed about the performance.More news: The other danger of the solar eclipse: distracted drivers
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