Vertonghen earns point for 10-man Ajax
Ronald Koeman's Feyenoord dominated the clash in Amsterdam but failed to capitalise after Jerson Cabral hit the bar and Ajax keeper Kenneth Vermeer saved with his foot a shot from Ruben Schaken.
Central defender Stefan de Vrij put Feyenoord ahead from close range after 61 minutes with a deflected shot and minutes later Ajax were reduced to 10 men following a red card for Vermeer who committed a professional foul on Guyon Fernandez.
Feyenoord remained fourth with 18 points after 10 matches, one ahead of Ajax who are sixth having failed to win any of their last five games.
AZ Alkmaar, 1-0 winners over 10-men Roda JC Kerkrade, remained top with 25 points, four clear of PSV Eindhoven and Twente Enschede, who drew 1-1 with Vitesse Arnhem and Groningen respectively.
Swede Rasmus Elm sealed Alkmaar's victory six minutes into the second half following a corner and Mark-Jan Fledderus was sent off for his second booking.
Wilfried Bony replied for Vitesse against PSV who had gone ahead through Tim Matavz, while Suk Hyun Jun salvaged a point for Groningen at home against Twente whose goal was scored by Ola John.