Louis van Gaal acknowledged Manchester United's difficulties in front of goal must be improved upon quickly following a 0-0 draw at home to West Ham United.
United failed to score for the third time in their last six Premier League fixtures on Saturday, with fans frequently demanding their team attack more in recent weeks.
The hosts produced 21 shots at Old Trafford but only one of them hit the target, and the manager feels greater composure is needed for his team to turn chances into goals.
"I think that we have seen a very good match with also a very good, organised West Ham United," Van Gaal told Sky Sports.
"We have created chances, we need to score, we must score but we didn't score and that's our problem.
"We can be very pleased with the second half but you have to finish because that is football, you have to score goals.
"You need also luck, but you cannot say it every time that we have to finish.
"The most important thing is that we are dominant, that we are creating chances. Then the other aspect we have to improve a lot because we don't score."
