Manchester United boss Louis van Gaal has claimed his side was undone by lack of luck in the art of converting chances into goals when they lost 2-1 at Swansea on Sunday.
The Dutch tactican also told Skysports after his side suffered their first defeat of the season that they could not cope with the tactical alteration of Ki Sung-yueng for Wayne Routledge in midfield.
"We controlled the game for 85 minutes but we lost in five minutes and that cannot happen," he told the BBC.
The switch to a midfield diamond was vindicated after just four minutes as Ashley Williams strode out of defence and freed Sigurdsson, whose precise cross found Ayew for Swansea's equaliser.
The hosts were ahead four minutes later, as Ayew's artful through-ball with the outside of his foot found Gomis, whose low finish beyond Romero sent the Liberty Stadium crowd wild and gave Monk the satisfaction of a tactical alteration paying off in style.
Van Gaal explained further: "They changed the shape and we had to be compact. We forgot that maybe because we are too dominant. We have to learn from that.
"First you have to create chances, with scoring goals you need luck, that we don't have at the moment.
"I have enjoyed our football but you need the result and we lost again. All the players were very motivated to beat them."
"The opponent changed their shape and we could not cope, that is not good.
"We lost in that five minutes and it is a pity because we controlled the game.
"You have to be compact, we were probably too dominant to have the sense to do that.
"We could have scored much more goals, that is not the problem. You need a little bit of luck."