A frustrated Louis van Gaal said Manchester United cannot challenge for the Premier League title after he watched his side "drop two points" in a 1-1 draw away to Aston Villa on Saturday.
United entered the day hot on the heels of second-place Manchester City after a six-game winning streak brought them within four points of their local rivals, but City defeated Crystal Palace 3-0 in the day's early game to open a seven-point gap.
With leaders Chelsea also seven points ahead with a game in hand, Van Gaal said United's chances of keeping up with the Premier League pace-setters are slim.
"We drop two points [but] we were the better team," Van Gaal said. "That's frustrating when you're better and you don't win. When you want to be a part of the title race, you have to win these games.
"I think also that we were not so aggressive in first half as we are usual, we kept the ball much better, but we didn't create so much because we were not looking to the forwards. That's why I changed [Darren] Fletcher for [Michael] Carrick, because I know he's more a passer to the forwards.
"But yeah, it was not good enough to catch the victory here. We were not creative enough in the second half. We didn't give the ball as good in the first half but had more aggression, so that was a plus, I think.
"OK, we have a draw, that's why I'm a little frustrated. We could have won this game in my opinion, and we didn't do it and we are responsible for that."
Asked if Manchester United could continue to challenge for the title, Van Gaal said: "No. You have seen you have to win these matches. We didn't win. But it is still a long time to go. Chelsea have to go to Stoke. It's not easy."
Van Gaal revealed that he watched the first half of City's game against Palace, which was goalless at half-time, but noted the ability to respond to adversity separates his side and the defending champions.
Asked if games such as Saturday's draw could cost United a title, Van Gaal said: "Yes. I have seen City in the first half against Palace and they could also have been behind in the first five to 10 minutes. They struggled until half-time, but at the end it is 3-0. That is the difference."
Striker Radamel Falcao scored in his first start for United, but the manager said that would not guarantee he stays in the lineup.
"It was a beautiful goal," Van Gaal said. "I liked him today. I'm very happy for him. And I am always happy when United scores.
"I have to compare every week. There's always a question, for every player, not only Falcao."