Tottenham boss Mauricio Pochettino accused his side of “arrogance” and “complacency” after a 2-1 loss at Southampton, which increased pressure on finishing in the top four.
Third-placed Spurs are without a win in their last four league games and are four points ahead of fifth-placed Arsenal, having played a game more.
Manchester United can draw level with Spurs if they win at Arsenal on Sunday.
“I am so, so, so disappointed,” said Pochettino, who sat in the stands.
“I am a little bit worried about this change from the first half to the second half – it’s only one thing, it’s mental.
“It’s about complacency, it’s about arrogance in a bad way. You can use the first half as an example of [positive] arrogance, playing with intention, focus, concentration – we matched them in everything and we were much better.
“And in the second half it’s the arrogance in a bad way. We need to blame all of us, the club.”