Manager Louis van Gaal has rued missed opportunities in Manchester United's 2-1 defeat at Swansea City this evening.

Juan Mata missed good chances before and after his 48th-minute opener, with quickfire goals from Andre Ayew and Bafetimbi Gomis ultimately condemning the Red Devils to a first defeat of the Premier League season.

Wayne Rooney, who struck a hat-trick in the midweek Champions League win at Club Brugge, also spurned a number of opportunities, and the Dutch coach admits that a lack of killer instinct cost his troops.

"We lost the game in five minutes and that cannot happen. The opponents changed their shape because we were 1-0 ahead and were dominating," he told MUTV.

"We could have scored more, maybe we should have.

"Nevertheless, they changed the shape and we didn't react as a team and were not compact enough in that moment so, in five minutes, we lost the game. It's a big pity we lost."

As a result, it was the Red Devils' third successive defeat to the Swans, who did a famous double over Van Gaal's side last term.