Louis van Gaal criticised Manchester United for a lack of composure after they drew 1-1 away to Chelsea thanks to a late Diego Costa equaliser.
United took the lead through Jesse Lingard just past the hour-mark but Costa turned home early in injury time to preserve the champions' unbeaten run under Guus Hiddink.
Van Gaal described the result as "unbelievable" given his side's performance but was left angered at the way they invited pressure in the closing stages.
"I think we played a superb game until the last quarter. Then we didn't keep the ball, or attack in the way I think we have to," he told Sky Sports.
"Chelsea were pushing with long balls, more aggression, but you have to keep the ball and be composed when you defend, not kick the ball away without any meaning. And we could have scored after the first goal, but you don't reward yourselves when you play such a game against a fantastic team like Chelsea.
"We were the better team but, again, we didn't win. It's unbelievable. We don't reward ourselves."
Van Gaal remonstrated with the officials just after the final whistle, and he admitted he was angry that referee Michael Oliver allowed Chelsea to take a corner beyond the allotted six minutes of additional time, only to end the game just as United looked to break.
"This referee gave them a lot of free-kicks at the end of the game," he said.
"The time was already over the six minutes and he let them kick the corner. Then, we had a free pitch, a lot of space, and he whistles. He did it in the first half also.
"You cannot do that. Don't let them kick the corner, the six minutes have passed. It's not fair on the two teams."
United are now six points behind fourth-placed Manchester City and Van Gaal accepted the race for the top three or four is looking increasingly difficult.
"When your aim is to be third, or second, or first, you need to win, because the gap is already big and it's now bigger. That's not good," he added.
"I know we have to play a very nasty duel against Chelsea and of course I will say to my players 'fantastic performance, until the last quarter'. But we have to reward ourselves. It's not the first time."