When Gus Poyet faced the media in the aftermath of Tottenham Hotspur's latest defensive shambles at Aston Villa on Tuesday his anger was palpable.

The assistant manager's message to the players pulled no punches. They had had their chances - heads would roll.

"This time it's enough - we have to change. It does not look like there is room for improvement so we have to change," he said after the 2-1 defeat in which both Villa goals followed slack marking at set pieces.

Manager Juande Ramos had indicated he would seek to bolster his defensive options during the transfer window. Ajax left-back Urby Emanuelson and Dani Jarque, the Espanyol centre-half, are under consideration and a deal has already been completed for Chris Gunter, the 18-year-old full-back from Cardiff City.

Poyet said the malaise was collective, with no one player culpable every time. "It's not about individuals," he said. "When, week in, week out, it's a different player, it becomes a team problem . . . so enough."

Ramos lost the defender Younes Kaboul to an ankle injury and replaced him with midfielder Jamie O'Hara in the 57th minute as he chased the game. Tottenham equalised through Jermain Defoe but with five minutes to go O'Hara was assigned to mark Martin Laursen at a Gareth Barry corner. O'Hara lost him and the Villa defender headed the winner. Laursen had been Kaboul's man and Ramos suggested O'Hara had inherited him.

Villa's opening goal had come when Kevin-Prince Boateng got in Michael Dawson's way and Olof Mellberg headed home.

Tottenham have repeatedly been undermined by goals conceded at set pieces and, although Ramos has tried to work in training with what he has got, injuries have brought further complications. Dawson was only just back from severe migraine problems at Villa Park but Ledley King had to be rested, having returned on St Stephen's Day from a lengthy lay-off after a knee operation.

Meanwhile, Ramos has dismissed suggestions that striker Dimitar Berbatov would be sold in the January transfer window.

"Obviously Berbatov's agent is looking to do his business and has been making comments," said Ramos yesterday. "But we are happy because we have the player on a contract and we plan to keep him."

Berbatov's agent had said earlier in the week the player would be prepared to leave Spurs if a big enough club made an offer. The 26-year-old has been linked with a move to Manchester United and Arsenal since signing for Spurs in July 2006. Chelsea coach Avram Grant could also be targeting the player after saying he admired Berbatov's skills.

But Poyet said no offer had been received for Berbatov.

"There is nothing happening. It is not a problem for us. He is here and it is no drama," Poyet said. "We want to improve and we want to go to a better level - he has to stay."