Manchester City manager Roberto Mancini was left "really disappointed" after his side lost in the final seconds at Sunderland in a game deemed must-win by the Italian coach.
City went into their match at the Stadium of Light buoyed by Manchester United's shock home defeat against Blackburn 24 hours earlier which presented them with a chance to open up a points advantage at the top.
However, in second-half stoppage time with the scoreline goalless, Ji Dong-Won, who replays show was offside, struck to hand Sunderland a famous win under their new manager Martin O'Neill.
"I'm really disappointed," Mancini told Sky Sports 1. "Second half we had a lot of chances to score. We didn't score, but we can't concede a counter-attack like this.
"We conceded two, three counter-attacks in the last 10 minutes which were really dangerous. A strong team can't concede this game. Sometimes when you can't win - because it was difficult - you can't lose.
"You need to defend those. Sometimes when you attack with seven players it's enough, because if not you can concede a counter-attack like we conceded.
"In the first half we didn't play very well, second half much better. We had to win this game. This moment is a strange situation."
Asked if that was good enough, Mancini replied: "No, not for a top team. In that situation, we attacked with eight players and the same players who attack need to come back and run quickly.
"I know football and for that reason in the last 15 minutes, I continued to call [central defenders] Vinny [Vincent Kompany] and [Joleon] Lescott to say, 'Stay there, stay there, don't leave the space', because that was dangerous.
"We continued to attack and sometimes we wanted to attack with 10 players. This is impossible. But that's it, it's finished. We have a game in 48 hours and we need to recover now.''
Mancini, who headed down the tunnel before the final whistle, admitted his side had been made to pay for missed chances.
He said: "It's frustrating because we can't lose a game like today's. In the second half, we had I don't know how many chances to score.
"But football is this. Sometimes you can't win. Sometimes you score three or four goals in a game, sometimes you can't score even if you have 10 chances to score.
"I am disappointed that we conceded a goal because a strong team cannot concede a goal like this.''