Striker Harry Kane said Tottenham had not learned from their mistakes, after they threw away a 2-0 lead against Olympiakos in the Champions League.
Despite leading through Kane’s penalty and Lucas Moura’s emphatic finish, last season’s beaten finalists were held to a 2-2 draw in Greece.
“You can see why the manager is frustrated,” said England forward Kane.
“He has been here for five years now and we are still making similar mistakes as we were the first year.”
Tottenham also conceded a 2-0 lead in the north London derby at Arsenal on 1 September, and Kane said the team had to improve.
“We are not young any more, we are not inexperienced. We have played in big games for club and country,” he added.
“We have to try to find a way to get around it and improve and get better. That is all we can try to do.”
Manager Mauricio Pochettino, who was appointed by Spurs in May 2014, questioned his team’s attitude.
Their next game in Group B is at home to German champions Bayern Munich on 1 October.
“We are conceding a lot of chances and lots of goals and we need to change that,” said Pochettino.
“The only way we can change is being more demanding from ourselves. That is the way we are going to approach the different days and be more consistent.
“Training needs to be harder. Psychologically harder.”
Pochettino said he was “very disappointed” and that his players “didn’t respect the plan”.
“That is what disappointed me most and that is what I told the players at half-time,” he added.
Former Tottenham midfielder Michael Brown said on BBC Radio 5 live: “I said last season that Spurs had done extremely well but unfortunately they’re just not going to be able to keep up with Liverpool and Manchester City, and that’s still the case.
“They’re just not at the same level.
“They’ve got some great individuals but as a team collectively, this keeps happening – they keep slipping up and conceding goals at the wrong time.
“We are being critical of Spurs and where they’ve come from, but they’ve got this new stadium and some good players. Can they keep progressing and not be this selling club?”