The Blues were dominant in the first half without ever really creating a clear-cup chance, but took the lead early in the second period when substitute Gerard Deulofeu provided a pinpoint cross for Romelu Lukaku to tap home.
The visitors rallied, however, and within a period of five minutes ten minutes after falling behind, were ahead and on their way to the fourth round of the FA Cup.
“In my opinion, it’s not bad luck – we did it by ourselves,” he said. “It was unbelievable how we dropped back after going 1-0 up and there was a lack of concentration.
“When I look at the equaliser, there was no pressing on the ball and we gave a fast player like [Ahmed] Musa a chance to score and he did that.
“We did the most difficult thing by scoring the opening goal because Leicester were playing very defensively. After scoring, I don’t understand why we lost the game, but if you play like we did after going ahead then you’re asking to concede goals.
“Everybody is disappointed. But we are still in a good position in the league table and I know that we need to change.”