Ajax's Eredivisie title hopes suffered a blow after Cyriel Dessers scored the goal that gave Heracles a 1-0 win on Sunday.
The 25-year-old, who recently stated his commitment to play for the Super Eagles, made the difference for the hosts with his effort in the 77th minute.
The goal extended Dessers' tally to 14 goals in 24 league matches and he stands as the top scorer in the Dutch top-flight.
Sunday's result was Ajax's fourth league defeat this season and it cut their lead at the top of the Eredivisie table to three points.