Manchester United suffered a miserable start to their Premier League campaign as Wilfried Zaha fired Crystal Palace to a shock 3-1 win at Old Trafford, while Arsenal struck late through substitute Eddie Nketiah to beat West Ham 2-1.
On a day of high drama Leeds edged Fulham 4-3 to earn their first top-flight victory since 2004 on Saturday and Everton went top of the table as Dominic Calvert-Lewin scored a hat-trick in a 5-2 destruction of 10-man West Brom.
On the second weekend of the new campaign, United were playing for the first time after being given an extra week of rest due to their involvement in the latter stages of last seasons Europa League.
But Ole Gunnar Solskjaers lethargic side were well below their best and Palace took full advantage thanks to Andros Townsends seventh minute strike and Zahas double against his former club.
There was a hint of controversy about Zahas first goal as VAR ruled Victor Lindelof had handled Jordan Ayews shot even though the ball was hit with force at him from close quarters.
David De Gea saved Ayews spot-kick, but VAR intervened again to order a retake as Uniteds keeper had strayed off his line and this time Zaha converted from the spot.
Uniteds only close-season signing Donny van de Beek came off the bench and the former Ajax midfielder reduced the deficit with a debut goal in the 80th minute.
But Zaha, who endured a difficult spell at United before rejoining Palace, showed why the Eagles are so keen to keep him amid speculation over his future as the Ivory Coast winger lashed home in the 85th minute.
For the first time in six years, United were beaten in their opening league game.
It was a chastening start to the season for United, who have come under fire from fans frustrated at their relatively modest transfer outlay compared to their title rivals.
Arsenal capitalised on the chance to open up a six-point gap over United in the battle for a top-four finish despite a poor performance of their own.
Alexandre Lacazette headed the Gunners into a 25th minute lead from Pierre-Emerick Aubameyangs cross.
But Mikel Artetas men were largely outplayed by the Hammers, who faced stinging criticism after a 2-0 home defeat to Newcastle on the opening weekend.
Michail Antonio levelled just before half-time and came close putting the visitors in front when his header came crashing back off the crossbar.
But Arsenal grabbed all three points five minutes from time when Dani Ceballos broke the West Ham offside trap and squared for Nketiah to tap home.
At Elland Road, promoted Leeds were involved in another eye-catching encounter in their first top-flight home match for 16 years.
After losing 4-3 at champions Liverpool on the opening weekend, Helda Costa fired Marcelo Bielsas free-scoring side ahead in the fifth minute.
Fulham striker Aleksandar Mitrovic equalised from the penalty spot but Leeds soon retook the lead with a spot-kick of their own, converted by Mateusz Klich.
Patrick Bamford and Costas superb strike looked have Leeds cruising to their first win back in the top-flight by the hour mark.
But Fulham pulled one back in the 62nd minute through Bobby Decordova-Reid and Mitrovics towering header four minutes later set up a tense finale.
Leeds opening games have seen 14 goals, which is the most for a top-flight sides first two matches since Wolves in 1962-63.
At Goodison Park, Evertons early-season optimism was not curbed despite falling behind to Grady Dianganas early goal.
Calvert-Lewin bundled home an equaliser before James Rodriguez put Everton ahead with his first Premier League goal and Albion imploded before the break.
Kieran Gibbs was dismissed for pushing James in the face in first half stoppage-time and then Baggies boss Slaven Bilic was sent to the stands after storming onto the pitch for a furious rant at referee Mike Dean.
Matheus Pereira equalised for Albion after the interval, but Michael Keane restored Evertons lead and Calvert-Lewin sealed the points with his second and third goals.
After a summer spending spree, Ancelotti is under pressure to deliver a big improvement on last seasons 12th place finish and the early signs are promising.
Having beaten Tottenham in their opening game last weekend, Everton have started a Premier League season with consecutive victories for the first time since 2012-13.
Im satisfied in front, we have to do better at the back, said Ancelotti.