Tottenham boss Mauricio Pochettino rued a missed opportunity as his side lost 2-1 to Monaco in the Champions League on Wednesday.
Spurs suffered a disappointing defeat in front of a record crowd as they started their campaign at their temporary European home of Wembley.
Monaco went ahead after just 15 minutes through Bernardo Silva and they doubled their advantage on 31 minutes when Thomas Lemar found the back of the net.
Toby Alderweireld pulled one back on the stroke of half-time but the home side could not draw level in the second half.
Speaking after the game, Pochettino said: "I think that we all agree that we started well but then we conceded after 15 minutes.
"We cannot concede in that way at this level, in the Premier League, the Champions League. It is difficult to accept how we conceded a goal in this way.
"When you concede like this it is very difficult. It is true that we had more chances, our positions, we were better than Monaco but they were more effective.
"Today was an opportunity to give to our fans a good victory and it is a shame for our fans."
The Spurs boss, who had never lost a European game at home with Tottenham before Wednesday night, described his side as having a "lack of passion".
He added: "I was speaking with my players at half-time. I think we needed more control in the centre of midfield, we needed to move Dele Alli up the pitch to be more aggressive.
"It is not new. I think we were better than Monaco, we need to win games, we need to be more aggressive with the ball.
"We need to play the way we are meant to play. They played in a very comfortable position.
"It is a fantastic opportunity, we have worked hard to be here and we need to be better.
"We need to work more on being aggressive, to show we are hungry on the pitch. In the second half I think we started well, but not well enough."