Dutch champions Ajax twice threw away a lead to lose 3-2 to AZ Alkmaar on the second day of the Eredivisie season.
Christian Eriksen and Siem de Jong gave Frank de Boer's side the lead on two occasions, but Roy Beerens and Aron Johannsson scored the equalisers before Viktor Elm's 74th-minute winner.
Feyenoord had an even worse Sunday as they were comprehensively beaten 4-1 at home to Twente - their second successive defeat.
The Rotterdammers were looking good for their first points of the season when Graziano Pelle fired them ahead. However, Kyle Ebecilio levelled before Dusan Tadic scored two penalties and Luc Castaignos rounded off the scoring. Feyenoord finished with nine men following red cards for Jordy Van Deelen and Stefan de Vrij.
On Saturday, 17-year-old Zakaria Bakkali scored a hat-trick as a very youthful PSV Eindhoven hammered NEC Nijmegen 5-0. The hosts' oldest player in the matchday squad, 22-year-old Georginio Wijnaldum, scored the other two goals.
PSV, PEC Zwolle, Utrecht and Heerenveen are the four teams who still have 100% records in the new Eredivisie campaign.