Eredivisie wrap: Ajax prove unstoppable
Siem De Jong bagged a brace, while Finnish debutant Nikolas Moisander, Tobias Sana and Thulani Serero also scored.
De Jong put the hosts ahead inside two minutes before recent signing Moisander, who made the return to Amsterdam Arena on Monday after spending four years at AZ, hit the back of the net nine minutes later.
Swedish winger Sana added a third for Ajax four minutes before half-time.
Serero and De Jong scored after the interval to cap a dominant performance against a NAC side languishing second-from-bottom.
Meanwhile, ADO Den Hag defeated VVV-Venlo 4-2 as they continued their unbeaten start to the season.
Marcel Seip handed VVV a 10th minute lead, however the visitors scored three goals without reply through Mike van Duinen, Tjaronn Chery and Jens Toornstra.
VVV reduced the deficit with 10 minutes left to play but Chery put the result beyond doubt with his second of the game.
And in Saturday's other result, PEC Zwolle netted a late equaliser to earn a share of the points at FC Utrecht.
Edouard Duplan broke the deadlock for Utrecht on the stroke of half-time but Darryl Lachman struck an 83rd minute leveller to clinch a draw.