The title challengers could not bounce back after Michail Antonio's early opener and threw away the chance to close on Leicester City at the summit
Mauricio Pochettino took some positives from his side's second-half performance despite seeing Tottenham miss out on top spot in the Premier League with a 1-0 loss at West Ham.
Spurs failed to make it a happy 44th birthday for their manager, paying the price for a below-par first-half display against Slaven Bilic's Champions League chasers.
Michail Antonio's fourth goal in as many home games proved the difference at Upton Park, his seventh-minute header from Dimitri Payet's corner settling the contest.
Tottenham were much improved in a second half they dominated, but struggled to create chances as they suffered a defeat that leaves them three points adrift of league leaders Leicester City going into Saturday's clash with Arsenal, who were beaten 2-1 at home by Swansea City.
Pochettino said: "The first half was poor, we never find the solution to play the way we normally play. In the second half we felt more freedom and tried to play and tried to create the chances and manage the game.
"I think that we made some mistakes normally we don't make. I think we repeated the first 20 minutes we played against Swansea [in Sunday's 2-1 win], it was difficult to start the game against Swansea.
"We were poor and our players know and are disappointed for that. The pitch doesn't help to try play the way we wanted to play and it was difficult to turn the result.
"It's not easy to play every week. We are on the top and we come from a very busy period that we play Europa League, FA Cup and now Premier [League] in one week - three games. Always it's tough but no excuse, only that we were poor in the first half.
"We need to be positive. Why not? In the changing room we can see the players are disappointed, the way they fight in the second half was fantastic.
"The second half I think we started very well, we deserved more in the second half, if we scored I think the draw was fair."
- Goal