The Tottenham Hotspur defender was understandably unhappy after the north London side's 2-1 defeat.
After beating the Premier League leaders 5-3, you wouldn't expect your side to lose to bottom-half opposition.
Yes, Tottenham were away at Crystal Palace; yes, Palace had a new manager in Alan Pardew and were looking to impress him; and, yes, the Selhurst Park atmosphere can intimidate the best of sides.
But Spurs were unbeaten in seven games in all competitions. Spurs had just beaten Chelsea convincingly. And Spurs had gone 1-0 up at Crystal Palace.
Mauricio Pochettino's men, however, contrived to lose 2-1 as Palace upped the ante and outclassed them in the second half.
Naturally, that left defender Jan Vertonghen frustrated - and the Belgian said his side were 'very stupid' to drop all three points.
“There is no point winning against Chelsea and then losing here. We have been very stupid to drop these points. Once again we have failed to jump up to fourth place," the Spurs man is quoted as saying by the Daily Mirror.
Tottenham's defeat, followed up by Arsenal's win the next day, leaves Pochettino's side sixth in the Premier League - three points off the top four.
Crystal Palace, meanwhile, sit in 15th after their win.