Haaland put City 2-0 up just before the hour mark at the Etihad Stadium with a spectacular acrobatic effort, the first of a brace that took the 24-year-old to 13 goals for the club this season and 44 in his career in 42 Champions League games .
Boss Guardiola said: “I know it’s not easy for him because they defend in the box, no space, three central defenders with him, two holding midfielders close to him, even the wings close to the holding midfielders.
“There is literally no room. Each cross is embraced and pushed. So it’s not easy.
“But I’ve talked to him a lot of times, ‘be patient, be positive, because the ball is coming, the ball is coming.’
“Today he scored two goals, (also) had two headers, really good, to score two more. Always Erling has this incredible capacity. He can touch 15 balls, 20 balls, but he has seven, eight chances.
“It’s unbelievable the talent this guy has and of course he scored a fantastic goal. (It was) quite similar to (against) Dortmund years ago with an incredible pass from Joao Cancelo. I don’t know which is more difficult – for me both.”
Guardiola agreed when told that comparisons could be made between Haaland and former Sweden striker Zlatan Ibrahimovic, saying: “Yes, his knack for doing it is quite similar, you’re right.”
City took the lead through Phil Foden in the third minute before scoring three times in quick succession after the break, with two Haaland finishes either side of John Stones’ header.
Mateus Nunes, who had two assists, then wrapped up the rout with a late penalty.
The Portugal international was making just his third start of the season and Guardiola added: “He’s a wonderful person. It has a specific quality. If you can run in transition, he’s as fast as Erling.
“It’s unbelievable when he runs 30-40 meters, nobody can stop him. That’s why we need him. He can play in many roles, his generosity in defence.
“The only problem he has is just one – his manager is maybe not giving him the minutes he deserves. But he is ready and can help us. It is important to have it.
“Both wings, Mateus and Savinho (who also contributed an assist), played really, really well.”
The result gave City seven points from three games in the league stage.