David Moyes blamed Manchester United's "terrible defending" for his side's 3-1 defeat at Chelsea, but said the scale of the loss was harsh on his team.
The Old Trafford boss felt his team dominated the opening period but were undone by sloppiness. Although Samuel Eto'o's opening goal was helped by a deflection, Moyes could not ignore the poor marking that led to the Eto'o completing a hat trick with two strikes either side of half-time.
"I would [say we dominated early on], but we got a bit unlucky -- the first goal took deflection but the other two, set pieces, terrible defending.
"I thought we played quite well today, especially in the first period, but we needed somebody to take on one of our chances. I thought the game would be tight, and I thought it was other than the two set pieces, which really changed the game. I think, apart from that, we had as many chances as Chelsea.
"Football's about scoring goals, and Chelsea did. We dominated the opening period of game, but if you defend the way we did at set pieces you don't deserve to win. We can only blame ourselves, no-one else."
"We won't throw the towel in until we can't get there [to top spot -- they are 14 points from leaders Arsenal]. The job is to try and finish first. I will keep trying to do that.
"Before today, we'd lost one in six in the league, and I didn't think there was a big difference between the teams today, not at all. The difference was our defending at set pieces. Nothing else."
He said he had known he was embarking on a "massive challenge" when he moved to Old Trafford last summer, and added: "It's a difficult task, but [it's about] perseverance and keeping doing what's right.
"We have players to come back, and this is a project I know that I'm going to improve as it goes along. I was hoping to win more and be competing a bit more than we've been, but that'll come."
Moyes argued that Nemanja Vidic's red card was undeserved, although he did not comment on Rafael's poor challenge on Gary Cahill.
"I don't think it's a sending off," he said. "I've not seen Rafel's tackle, but [Vidic's] is not a sending-off. I think it was just a bit of tiredness, but not a sending off."
The United boss accepted that retaining the title now looked unlikely, but said the club would not be rushed into transfers.
"It's a long way away," Moyes said of top spot. "I'd never say it's gone, and we'll do our best to try and get back into it."
He said transfer market decisions would not be taken "because of results" and explained: "The club have always said it's a long-term [project], and they know it's a job to be done."