Vital errors, missed chances and a disallowed goal left Sam Allardyce hugely frustrated as West Ham United were edged out 2-1 at Manchester United.
The Hammers yet again produced an eye-catching attacking performance at Old Trafford, highlighted by Diafra Sakho's fourth goal in four starts, only for two early goals and Kevin Nolan's disallowed late strike to leave them pointless.
West Ham dominated the second half, both before and after Wayne Rooney's sending-off for a wild kick on Stewart Downing, but ultimately had nothing to show for their efforts.
Speaking to West Ham TV, Big Sam lamented the circumstances which combined to condemn his side to an unwarranted defeat.
"There were three main factors - one is that we gifted Man United two goals when we shouldn't have done. If you gift that quality of player a chance, as we did on both occasions, then they will punish you.
"They were good finishes by Wayne Rooney and Robin van Persie but that is why they pay millions and millions of pounds for them.
"We've created more chances than them, but we haven't taken those chances and that's the second reason why we've lost the game. We created chance after chance after chance, particularly after their first goal when Enner Valencia got a clean shot at goal from 12 yards out with only the goalie to beat and he blasted over the bar, then after we got back to 2-1.
"I'm a little sick on that basis, then thirdly we have the decision at the end with Kevin Nolan's goal which I've looked at four times and we now know was the wrong decision.
"We leave Old Trafford extremely frustrated, having played well, but that means absolutely nothing to me because we didn't get anything from the game. The game is about getting the result but we've lost and that's more our fault than the assistant referee's.
"He's made one crucial decision that's wrong, but we made two bad decisions and they scored two and missed too many chances to get back to 2-2 before the assistant referee's mistake."
While the manager was rightly annoyed with the decision to disallow Nolan's 89th-minute tap-in, he felt the decision to send-off Wayne Rooney just before the hour-mark was justified.
"We'll have to see what [PGMO chief] Mike Riley says about it, but I'm sure he'll say it was reckless and if it's reckless and dangerous then it's a red card.
"Wayne made it too obvious. Instead of doing what some players do when their opponent gets away from them, which is just trip them up and get a yellow, he just hacked him down. It looked pretty bad from where I was."
While naturally disappointed to see his side lose on the road for the first time this season, Big Sam was content to see Sakho score for the fourth consecutive game.
The Senegal striker nodded in when James Tomkins' header from Stewart Downing's corner bounced back off the crossbar and later saw a superbly controlled second-half volley saved by David de Gea.
"Sakho is looking great, isn't he? He could have had a hat-trick and he has scored again. He had a volley on the far post which was beautifully saved by De Gea and a header on the far post which he could have done better with.
"Him and the other lads have had enough chances. A couple have just gone the wrong side of the post and stuff like that, but when we finally broke the then men down the goal was disallowed. We know how hard it is to break ten men down because we won with ten men ourselves twice last season."
The manager was also asked about the performances of full Barclays Premier League debutants Diego Poyet and Morgan Amalfitano, who were drafted into the starting XI due to injuries to Mark Noble and Cheikhou Kouyate.
"They did OK. I think Morgan is finding is feet after joining us on the last day of the transfer window, so he still isn't 100 per cent match-fit, and it's the same with Alex Song. Mark has a calf injury and Cheikhou is going to be out for a while, as we know, so they did all right.
"We just didn't do well enough in the first 25-30 minutes, but we got back to 2-1 and we had chances to get a point. Once we scored, we found our feet and the team responded well after a miserable start. They showed what they are made of, so from that point of view I was really pleased with how we stuck at it."