Erling Haaland scored twice on his Premier League debut as Manchester City opened their defence of the title with a 2-0 win at West Ham, while Manchester United were beaten 2-1 by Brighton in Erik ten Hag's first game in charge on Sunday.
Haaland lived up to the hype since his transfer from Borussia Dortmund to give the champions a perfect start to the season in the searing heat of East London.
West Ham nearly derailed City's title chances when they led 2-0 at half-time in the penultimate game of last season before Pep Guardiola's men battled back for the point that ultimately edged out Liverpool at the top of the table.
But they were no match this time as Haaland immediately proved the value of City adding a proven goalscorer to their arsenal.
The Norwegian has been signed as the long-term successor to Sergio Aguero and started his City career just like the club's all time record goalscorer with a double on his league debut.
Haaland had missed chances in City's 3-1 defeat to Liverpool in the Community Shield, but Guardiola's warning that the goals would soon flow proved to be correct.
"We know we have a threat there. He is an incredible deep runner and finisher," said Guardiola.
"He is adapting perfectly in the way we want to play. We are going to find him more and more and hopefully we can give him the opportunity to score more goals."
City's patient possession game wore the Hammers down as temperatures in the English capital soared above 30 degrees celsius on Sunday.
Haaland took responsibility from the penalty spot to open his Premier League account after he had been brought down by Alphonse Areola.
West Ham started the second half with more attacking intent but that simply played into the hands of City's new weapon as Kevin De Bruyne split open their defence with one pass on the counter-attack for Haaland to gallop clear on goal and slot low past Areola.