The Blues conceded from a long-range shot from Harry Kane to make it 1-0, but the second and third goals were down to individual players making mistakes or switching off, which left the Dutchman frustrated.
He said, “At 2-1 I was really optimistic about getting one. But the players were a little bit afraid and did not have that ball possession that they have had before.
“At 3-1, we brought it back again but there was no time to make a draw.
“Tottenham are a strong team. Now is the time to keep calm and prepare for the next two home games. That will shape our direction for the end of the season.
“The game was really difficult. We started well and made it hard for Spurs to create open chances, but they have scored from a shot from distance. After that it was more difficult.
“They had further chances to score before half time, and what really disappointed me was how they got their second goal, from a mistake by us.
“At least we showed great character until the end of the game, and tried to get it back at 2-1. We were hoping for a point but their third killed the final result. It was too easy from the free-kick and if you make that kind of mistakes at this level against a team like Spurs then they will punish you.”