Louis van Gaal said Manchester United had nobody to blame but themselves after they were held to a 3-3 draw by Newcastle on Tuesday.
Wayne Rooney and Jesse Lingard scored in the first half to put Man Utd 2-0 ahead and Rooney restored the lead in the 79th minute after Newcastle fought back to 2-2.
Lingard and Marouane Fellaini both wasted excellent chances to add to the visitors' tally and they paid the price as Paul Dummett scored a last-minute equaliser for a share of the spoils at St James' Park.
"We are very disappointed," said Van Gaal. "But we have to blame ourselves because we could have finished this match much earlier with big chances from Lingard and Fellaini and we didn't do that. I have said that to my players too.
"The deflected shot from Dummett was luck for Newcastle, but you have to force the luck and finish the chances you get. Certainly when they are so big."
Man Utd looked to be heading for a third straight win in all competitions after opening up a 2-0 lead inside 40 minutes.
But they were pegged back by Georginio Wijnaldum's goal before the break and then a penalty from Aleksandar Mitrovic after he was adjudged to have been fouled by Chris Smalling at a corner.
"You can say the referee makes a decision with the penalty that is maybe a big question mark, but we could have finished the game ourselves much earlier," said Van Gaal.
We have scored three goals and have one point, nothing more. I have said in all my press conferences that you have to score one more than your opponent, we didn't do that today.
"We have a fantastic defence but we conceded three goals, now is the defence weak? No, we were unlucky in the decisions of the referee and a deflected shot, and we didn't finish our chances."
While Van Gaal was critical of his side's finishing, he was also disappointed with the awarding of Newcastle's penalty.
"The heavyweight wrestling between Mitrovic and Smalling, you can clearly see that he [Mitrovic] is pushing the head of Smalling to the ground," he said. "Then it is about heavyweight champions and who is the heavyweight champion at the end of it, and that was Smalling in his eyes. I cannot understand that."