Tottenham manager Mauricio Pochettino tore into his players after their Champions League dream was dealt a huge blow against Ajax on Tuesday night.
Spurs face a huge task if they are to reach the final in Madrid on June 1 after Donny van de Beek's first-half goal handed the Dutch club a slender advantage ahead of next week's second leg in Amsterdam.
Spurs were forced to ride their luck - Ajax hit the woodwork while Hugo Lloris made an excellent stop to deny a Van de Beek brace.
And Pochettino couldn't hide his disappointment, saying: 'In the first half we started really not in a good way.
'My feeling is they were more proactive, showed more energy and it was difficult for us to play. The way we conceded was so painful - in the first half hour we struggled.
'Our lack of energy, that made our game difficult. In the second half we pushed them, tried to create some chances. We had a lack of aggression and sloppiness.
'Today wasn't our best game. We all agree that we cannot start the game like that.
'But we are alive and we need to believe we can go there and win the game. The second half gave us hope for the second leg.'
Having started with a back-three, Pochettino reverted to a back-four before half-time.
And the Argentine admitted: 'Watching now, I can accept it was a mistake to start (with a back three).
'I am not happy. But you cannot guess that if we played in a different shape that we maybe play in a different game.
'That's about our approach not being good. That's my responsibility as I'm the manager.'