Juan Mata believes Manchester United were only beaten in a five-minute period at Swansea City on Sunday.
The Red Devils led early in the second half thanks to Mata's goal but were hauled back in when Andre Ayew levelled on 61 minutes before Bafetimbi Gomis' eventual winner in the 66th.
After the match, Mata felt it was a poor lapse by he and his teammates during that time which in the end cost them the game.
"It is a big disappointment," he said. "We did the most difficult thing, which is score first.
"We put ourselves ahead in the result, then in five minutes we lost the game.
"They changed the shape so we didn't react quickly enough. They created two quick plays and scored two good goals."
Mata added: "We are disappointed because we knew we had to learn a lesson from last season.
"We did the same – we scored first then lost the game, and we are very disappointed.
"We created chances, especially in the first 15, 20 minutes. We played great football, but after that they came into the game and put pressure on us."