Video - Spurs fluff their lines as they bid to claim top spot
Tottenham manager Mauricio Pochettino suffered a miserable 44th birthday as his side slipped to a rare defeat against West Ham in the Upton Park rain.
Michail Antonio's first-half goal condemned Pochettino's in-form side to a 1-0 defeat, their first away from home since the opening day.
Spurs knew victory would take them above Leicester to the summit for the first time this season, as well as send out a huge statement in the race for the title.
Instead, they ran into a West Ham side determined not to give their fierce rivals a reason to celebrate in the final London derby under the lights at Upton Park.
“I think that we didn’t start the game in a good way. We made some mistakes and the team didn’t feel free to play the way they play," stated Pochettino.
"West Ham is a strong, physical team which made it difficult and the conditions favoured them because the pitch wasn’t good.
“We need to be positive and it is important to be ready for Saturday. When you lose you can blame that the players are tired or whatever but the reality is that it was just a bad night for us to play the way we play tonight.
"We were poor in the first half, we know. We are very disappointed. But the way the players fought in the second half was fantastic."
West Ham's win moved them to within a point of fourth placed Manchester City, but their manager Slaven Bilic is not dreaming about Champions League football just yet.
“We are not thinking about the top four," he insisted. "The gap might be small for those places but there is also a small gap between us and ninth place.
"We are going to continue to play like this and try to win every game.”
A spirited second half showing by Spurs should send them into Saturday's north London derby against a fading Arsenal side in good heart.
If they win that game, Pochettino's side will claim top spot in the Premier League, even if it is only for a few hours until Leicester take centre stage once again.