Jamie Vardy and Riyad Mahrez scored stunners to leave the Foxes two goals to the good by half-time and, despite Harry Kane scoring as part of a late onslaught from the visitors, Spurs fell to a first Premier League defeat at the King Power Stadium.
Tottenham have now lost three consecutive league games for the first time since March 2014 and boss Pochettino has noticed a worrying trend in matches.
"We did not play in the way we normally play. The first half was a poor performance and it was difficult after that to get back into the game," he told BBC Sport.
"We feel very disappointed in our performance. We started the game not in the right way and we conceded the opportunity to them to score.
Christian Eriksen and Fernando Llorente each missed great opportunities either side of Harry Kane's goal, while Danny Rose was denied a last-gasp penalty with referee Anthony Taylor deciding he had not been fouled by Wilfred Ndidi.
But Pochettino was reluctant to speak about the decision, adding: "I don't know. I said last week I don't want to speak anymore about the decision of the referee."
One positive for Spurs, who will be 16 points off the top of the table if Manchester City beat Southampton on Wednesday, was the return of winger Erik Lamela after over a year on the sidelines having undergone surgery on both hips.
The Argentina winger laid on the assist for Kane and Pochettino is confident Lamela has a big part to play going forward.
"His quality will be important for us in the future," he said. "I am happy for him to play 15 minutes."