Louis van Gaal admits he is "worried" about Manchester United's lack of goals after their 0-0 draw with PSV on Wednesday night.
United's goalless draw in the Champions League leaves them in second place in Group B, just a point above PSV in third and facing a trip to first-place Wolfsburg in the final game.
A win against the German side would see United finish top of the group but if PSV win at home to bottom side CSKA Moscow, a defeat or draw for United in Wolfsburg would see them drop out of the competition and into the Europa League.
United have scored just five goals in their last seven games in all competitions, and Van Gaal said: "Of course I am worried [about the lack of goals], but I know also goals are coming and going. It's not a consequence of good performances and bad performances.
"Also today we could have scored at least three goals. They were not the most difficult chances, but we didn't score and the next game you can score out of nothing. That's football.
"We are still second so we are still in the qualifying position I believe. We have to do it in Wolfsburg. That's more difficult, it [would have been] much more easier to do it tonight.
"Now our efforts in away games is much better than last year so we have to do it in Wolfsburg.
"We have won also our home match against Wolfsburg so why we can't win in Wolfsburg? Our away efforts are much higher than last year as you know."
United struggled to break down a dogged PSV side throughout the contest and having left Juan Mata on the bench, Van Gaal did not bring the Spaniard on until the 85th minute.
When asked why he did not introduce Mata earlier or even start the midfielder, Van Gaal insisted he played the team he believed had the best chance of winning the crucial clash.
He said: "That is always the question after disappointing results, then you are coming with these kind of questions. But I thought that with this line-up we had the best chance to win.
"You shall not know if it was with Mata in the beginning happening. You'll never know, but you as a journalist you are thinking, 'Yeah, it is like that'. But I can say that it is not like that."