Alex Ferguson admitted that a draw with Marseille in the first leg of the Champions League round of 16 could be a "dangerous result".
The "Red Devils" in France did not concede a goal, but also left with a blank - the match ended 0-0.
"The result is not bad, I think it is fair," said Ferguson. "The opponents did not give us much trouble attacking - they only struck once at goal.
"Overall, there weren't many incidents in the match, so it wasn't beautiful. But such a result can be dangerous if we concede a goal at home. Still, everything is very simple - if we win, we will advance to the next stage."
And added: "In Manchester, we will attack much more, because this time Marseille tried not to lose."
Meanwhile, the coach of the French champions, Didier Deschamps, said: "Half of the work is done. We did not concede a goal, although maybe we could have attacked a little more at the end of the match.
"We know that it will be much harder away, but our hopes are still alive."