Isak has missed four games for Liverpool in recent weeks due to a groin injury. When he returned to the team's squad, it was zero minutes and a big loss for the reigning champions.
Erling Haaland had the chance to open the scoring from a penalty in the 13th minute, but Liverpool goalkeeper Giorgi Mamardashvili was able to save the striker's weak attempt.
Instead, the Norwegian broke the deadlock a quarter of an hour later when he headed in Matheus Nunes' cross and scored his 13th Premier League goal of the season.
In first-half stoppage time, Nico González made it 2–0 for the home team, before Jeremy Doku completed the scoring in the second half with a delicious shot from outside the box.
Liverpool had their chances, but their shots either went wide or into the hands of City goalkeeper Gianluigi Donnarumma. The away team had the ball in the net at 0–1 down when Virgil van Dijk headed in a corner, but it was ruled out for offside.
City coach Pep Guardiola played his 1,000th match as a football coach on Sunday, reaching the milestone in the best possible way.
Manchester City is now second in the Premier League, Liverpool eighth.
