Ledley King has admitted Tottenham need to learn lessons from the loss to Manchester United after seeing defensive mistakes punished.
Spurs appeared to be on top during the first half of Sunday's game at White Hart Lane but fell behind on the stroke of half-time when Wayne Rooney headed in Ashley Young's corner.
Tottenham tried to respond at the start of the second period but a quick-fire double from Young sealed victory for United, with the final score 3-1 after a late Jermain Defoe consolation.
While United took their goals well, King was left frustrated by the lapses in concentration that allowed them to happen.
And the centre-back has called on his team-mates to keep their focus in future to avoid suffering such painful defeats.
"It's tough to take because I thought for the majority of the game we gave a good account of ourselves," King told the club's official website.
"But if you fall asleep at vital times you will get punished.
"We conceded the first goal at a bad time. That was disappointing, a free header in the six-yard box shouldn't be happening.
"We tried to regroup, tried to come out and perform again, tried to lift ourselves and we did that, but went to sleep on a throw-in.
"You won't beat teams like United unless you are fully concentrated for the full 90 minutes, and that was a bit of a lesson.
"You can't fault our work-rate but it's those moments that make all the difference."