Haaland has netted just three goals in his last 12 Premier League appearances, having scored 19 in the first 17 of the season.
He failed to find the back of net against West Ham United as his dire form continues in what is a major lull for the Norwegian striker.
City manager Pep Guardiola spoke on his struggles this week and vowed that he will return to his best.
"Erling knows we need his goals," City manager Pep Guardiola said. "We need to create more chances for him too, but he had three or four good chances early in the first half and didn't score.
"But it's not just about him. It's about all the players, the vibes they feel. But he will be back. Erling will be back and maybe soon too."
Aguero backs Haaland
Now, speaking to Stake, Aguero has stood by Haaland who he thinks is offering more to the club than ever despite a lack of goals.
“It’s true that (Erling Haaland) has scored fewer goals, but I think he’s made huge progress in his team play.
“He holds the ball up more, he assists, he defends. He’s a more complete player now.
“And even though he has scored fewer goals, the team hasn’t stopped scoring. Semenyo’s case is just one example.”
Haaland's last goal came in a 3-0 win over Fulham in February and he will hope to return to his best as City try to make a comeback against Real Madrid who they trail 3-0 to thanks to a poor first leg.