Manchester - Manchester United defender Chris Smalling admitted his team's first-half performance had been unacceptable after they overcame Burnley 3-1 to reclaim third place in the Premier League.
The centre-back scored two goals, the first within 22 seconds of coming on as a fifth-minute substitute, but Louis van Gaal's side were outplayed for most of Wednesday's first half by their relegation-threatened visitors.
"The first half, we have to look at ourselves and make sure it never happens again," said Smalling.
"Obviously, it's a good run we're on at the moment, but the manager just said in there that the first half was unacceptable and I think all the players know that.
"If we can keep winning games playing that badly, then it shows that when we do play well it will all click and there will be much better performances at Old Trafford, that's for sure.
"It wasn't a 3-1 scoreline game, especially the first half. We let ourselves down from one to 11. We've got to play much better."
United have now lost just once in 18 games, despite disquiet among fans about their style of play and the much-publicised allegation that they adopted a 'long-ball' approach in Sunday's 1-1 draw at West Ham United.
But they required two set-piece goals from Smalling, either side of a Danny Ings equaliser, and a late Robin van Persie penalty to see off Sean Dyche's battling side.
"It was pretty unreal," said Smalling, of his first ever two-goal performance.
"I was quite fortunate. When you come on as a defender, it's never easy. But if you have a corner, it puts you on the front foot straight away and I was lucky I got free."