Jose Mourinho felt United's home draw with Stoke could easily have been a walkover but refused to criticise his side's finishing.
The Potters came to Old Trafford at the foot of the Premier League table and with the worst goal difference in the division, minus 11, but United were unable to punish them and had to settle for a 1-1 draw.
Substitute Anthony Martial curled into the corner moments after stepping off the bench and Stoke's Joe Allen rammed home from close range eight minutes from time to equalise.
Paul Pogba had three wonderful chances to find the net, heading the best against the crossbar in the closing minutes, while Zlatan Ibrahimovic and Jesse Lingard also failed to beat the impressive Lee Grant.
"I'm happy with the performance but when the result should be 5-0 or 6-0 and it is 1-1 then the happiness disappears," said Mourinho.
"I think it was our best performance in terms of the football we played, the creation of chances, the consistency.
"In this moment it should not be just three points but a fat result.
"From minute one everything was beautiful. The first chance, the one Paul missed, was beautiful football.
"In the second half he hits the post (crossbar), the save down low in the corner...beautiful football.
"I'm very frustrated but the performance was there."
Mourinho is not always forgiving when his teams falter but on this occasion he praised 33-year-old Grant, on loan from Derby, rather than highlight flaws in the home dressing room.
"I never criticise my players for missing chances. Their goalkeeper was man of the match, deservedly," he noted.