Marouane Fellaini has admitted Manchester United have struggled to find the balance between defence and attack this season.
United conceded two goals to West Bromwich Albion on Monday, when midfielder Fellaini belatedly opened his account for the club, and had let in four against Milton Keynes Dons and five when they visited Leicester City.
Manager Louis van Gaal has often discussed their difficulties getting the right balance and Belgium international Fellaini agreed.
"We know we have a problem with the balance between defence and attack, but we train all day to try and make it better," he said in the Daily Mirror.
"We offered too much space in defence [in the 2-2 draw against West Brom] but next week is a big game and we have to learn to focus for the whole game. I am determined to get things right; that is why we play football."
United's next two opponents are Chelsea and Manchester City and Fellaini added: "I don't think it was a good result for us [against West Brom] because the next two games will be difficult."
Fellaini came off the bench to replace Ander Herrera in a half-time switch and scored his first United goal three minutes later.
He explained: "The manager asked me to put pressure on the box and to keep fighting. I did that and I managed to score.
"It was a good feeling -- I have waited a long time to score my first goal for Manchester United and I hope to score more."