London - Tottenham Hotspur manager Mauricio Pochettino blamed the mentality of his players after Newcastle United overturned a first-half deficit to win 2-1 at White Hart Lane in the Premier League on Sunday.
While a second successive victory for resurgent Newcastle pushed them out of the relegation zone and towards mid-table, Tottenham are faltering.
Emmanuel Adebayor's header gave the hosts the lead but Sammy Ameobi scored eight seconds into the second half with his first touch after coming on at halftime before Ayoze Perez completed the turnaround.
"It's a big blow for us. We deserved more, but we made one or two big mistakes and it's difficult to win the game," said Pochettino, whose side had sparkled in a 5-1 midweek victory over Asteras Tripolis in the Europa League.
"It's not easy to compete in the Europa League and Premier League. Today it was about a lack of concentration at the start of the second half and then the head is gone.
"It's hard to get the concentration. We need to improve a lot. It's not tactical or physical, it's our mentality."
Defeat left Tottenham, who have been regular contenders for the top four in recent seasons, down in 11th place with 11 points from their opening nine games.
Newcastle, despite no wins from their first seven games and with manager Alan Pardew under fire from the fans, are only a point behind in 14th spot.
Pardew said he had given his side a dressing down at the interval after they allowed Tottenham to dominate.
"In the second half we came out with more purpose. It was a massive result. It was a real team effort," he said.
"At halftime I was pretty angry. Sometimes in the Premier League when you're dominant like Spurs, but only a goal up, you lull them (into a false sense of security)."
Pardew's decision to introduce Ameobi and Remy Cabella, whose cross allowed Perez to head the winner after 58 minutes, proved a masterstroke and he could not resist a sly dig at the fans who have been calling for his head all season.
"At the moment the Geordie nation doesn't think I'm good enough. I've been here for 701 games now," he said.