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Southampton 2-1 Tottenham: Top four scrap is now Spurs reality - Pochettino
Tottenham boss Mauricio Pochettino says his side "did not take the second half seriously" in their 2-1 loss at Southampton and they are now under pressure to finish in the top four.
Third-placed Spurs are without a win in their last four league games.
They are just four points ahead of fifth-placed Arsenal, having played a game more than their London rivals.
"It is difficult to understand why we changed so much from the first half to the second," said Pochettino.
Speaking to BBC Match of the Day, he added: "We were better at everything but we lost the game. We did not take the second half seriously."
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Report: Southampton 2-1 Tottenham
What happened in the Premier League on Saturday
Pochettino's side led at the break through Harry Kane's 200th career goal but Yan Valery and James Ward-Prowse scored in the space of five minutes to complete the turnaround.
Spurs are nine points adrift of second-placed Liverpool, who have a game in hand, and eleven behind league leaders Manchester City.
And Manchester United - currently in fourth - will go level on points with them if Ole Gunnar Solskjaer's side can beat Arsenal at the Emirates on Sunday.
Mauricio Pochettino watched Saturday's match from the stands as he serves a two-match touchline ban
"I am very disappointed but this is our reality," Pochettino added.
"People talk about perceptions but we need to realise if you do not fight with intensity for the Champions League, you will struggle.
"The reality is you cannot only play for 45 minutes - we are a Champions League team, in the quarter-finals. The team does not have the experience of competing in these circumstances, so it is good to learn but we have to fight every single opponent.
"We are fighting against big sides [for the top four]. We had a big gap - welcome to the reality - and we are under pressure to win games. It is a massive challenge for us."
Tottenham have now not won a game in the Premier League since they beat Leicester nearly a month ago. However, they did advance into the Champions League quarter-finals by beating Borussia Dortmund home and away.
Source: bbc.com