There were goals galore in Netherlands' top flight this weekend, as Groningen continued their fine start to the season, while RKC edged a six-goal battle with Vitesse
Ajax slipped to their first defeat of the season as a late goal from Viktor Elm gave AZ a 3-2 win on Sunday.
Elm volleyed home with 16 minutes remaining to give the hosts their first points of the Eredivisie campaign in an entertaining encounter at the AFAS Stadion.
Defending champions Ajax, who finished the match with 10 men, went ahead after 21 minutes from a Christian Eriksen free-kick, but Roy Beerens levelled from close range just a minute before the interval.
Ajax reassumed control 14 minutes into the second half, Siem de Jong heading Bojan Krkic's right-wing cross into the bottom corner.
But the game turned seven minutes later as Aron Johannsson equalised from the spot after Ajax right-back Ricardo van Rhijn had been dismissed for bringing down Nick Viergever.
Frank de Boer's men attempted to cling on for a point, but their hopes were ended as Elm met substitute Maarten Martens cross to seal victory for AZ.
Feyenoord are still awaiting their first win after they had two players dismissed in a 4-1 home defeat to Twente.
Graziano Pelle powered home Jordy Clasie's corner after 29 minutes to give Feyenoord the advantage at De Kuip, but Kyle Ebecilio tied things up for Twente eight minutes later.
Ronald Koeman's men did not lose at home last season, but they fell behind after 58 minutes, debutant Jordy van Deelen shown the red card for felling Shadrach Eghan, allowing Dusan Tadic to convert from 12 yards.
Feyenoord were reduced to nine soon after, with captain Stefan de Vrij shown a second yellow card for a foul on Luc Castaignos.
Twente duly took advantage as Tadic netted his second penalty after Joris Mathijsen tripped Dico Koppers, before Castaignos rounded things off with a cool finish 11 minutes from time.
Groningen maintained their 100 per cent record with a comfortable 2-0 win over Utrecht at Euroborg.
Nick van der Velden put the hosts in front from the spot after just two minutes, 16-year-old striker Richairo Zivkovic netting his second goal for the club to clinch the win midway through the second half.
Elsewhere, RKC won a six-goal thriller as they beat Vitesse 4-2 at the Mandemakers Stadion.
Kelvin Leerdam put the visitors in front as he turned in Theo Janssen's corner after three minutes, but Robert Braber and Romeo Castelen turned things around for RKC.
Valeri Kazaishvili made it 2-2 nine minutes into the second period.
Captain Sander Duits ensured success though for RKC, scoring from the spot after Jan-Arie van der Heijden fouled Castelen after 74 minutes, before curling home an excellent free-kick to clinch the match.