It was the most important match of the season so far for both Arsenal and Manchester City at the Emirates Stadium in London.
Then the home team got off to a heavy start.
Arsenal defender Takehiro Tomiyasu was supposed to pass home to goalkeeper Aaron Ramsdale, but the pass was not hard enough.
Instead, Kevin De Bruyne was able to lift the ball in for 1-0 to the visitors.
Bukayo Saka equalized at 1-1 on penalties in the first half, but in the second City were outnumbered.
Jack Grealish scored 1-2 and then the Norwegian Erling Braut Haaland stepped into the proceedings and scored his 26th goal in the Premier League.
City, thanks to the victory, moved past Arsenal in the table into the lead by virtue of a better goal difference.
Watch Tomiyasu's blunder in the clip above.