Sven-Goran Eriksson blamed Leicester's poor start to the second half for the 3-2 home defeat against Norwich.
The Foxes began the second half at 1-1 after goals from Wes Hoolahan and Richie Wellens but within 15 minutes of the restart, they were chasing the game as Norwich raced into a decisive 3-1 lead. Grant Holt, from the spot, and Aaron Wilbraham were the scorers, with Paul Gallagher getting Leicester's second in injury time.
Eriksson, whose side are now seven points from the play-offs, said: "It was very bad, I think. We all thought at half-time that we could win the game and then it was 3-1 more or less after 15 minutes. We weren't even second to anything. We didn't win any challenge, second ball or anything."
He added: "We let them have the ball and do what they wanted. I do no know why we started the second half with no energy at all. It was extremely disappointing. I have not seen this team like that before.''
Norwich manager Paul Lambert hailed the win as the Canaries' best performance of the campaign.
He said: "That's as good as we have been this season. We dominated from start to finish away from home and in front of a vibrant crowd. We thoroughly deserved to win.''
Lambert insisted Norwich had the pedigree to maintain their promotion push.
"We have surpassed what we thought we could do," said the former Celtic midfielder. "The three-year plan was to survive in this league. Now we have as good chance as any - QPR, Cardiff, Leeds and Swansea - of going up."
The Canaries boss also saluted goalscoring midfielder Hoolahan.
"Hoolahan was unplayable," he added. "Leicester could not get near him. His performance was outstanding. It was right up there with the best he had produced."
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