Since Liverpool is not a weak team, I immediately think that Haaland should be fielded from the start of this match. There's no reason to weaken the squad temporarily because a tough opponent can always seize that opportunity as soon as the first half whistle blows. Doku might be a potential substitute to replace Haaland, perhaps around the 60th or 80th minute, to refresh the attacking line.
Actually I think Alvarez will replace Haaland because there are more players that can play in midfielder, Manchester City only have Rico Lewis and Oscar Bobb as substitute players lol. I have not yet see there's a club which lack of player because most of them are injured, so they only have 9-10 players which is not enough.
Halaand is irreplaceable in that Manchester city team at the moment. He’s definitely starting that game. City have some injury concerns; like Ederson, Matheus Nunes and Nathan Ake all withdrew from international duty, while Rodri missed Spain's win over Cyprus after feeling uncomfortable. I think Halaand also withdrew from the squad after damaging his ankle on international duties so I expect him to be fully fit for Liverpool clash. Although the absence of Haaland does not give a down fall for Manchester city. They have playing very well even without their midfield talisman Kelvin Debruyne, as for me I am very sure that Liverpool cannot take full 3 points at Etihad stadium.