I have been thinking about the drop in Haaland's form recently. First of all it is totally normal for any player of course. I have been just thinking about whether there could be a special reason affecting it as well. De Bruyne's absence came to my mind after that. The reason why is that there was a great relationship between these two players. 
De Bruyne was sending a lot of balls to Haaland to make him more active and effective in the attacking line. You know how great De Bruyne can pass the balls to his teammates. He is like a magician. I hope that Haaland can reach his usual level sooner or later. I'm still contented with his goal effort so far of course. But I would like to see him doing good during the full season as well.Obviously, Manchester City's performance is not the same as last season, which I believe is due to the absence of one of their key players, De bryune, whose absence affects the squad honestly. However, Halaand's performance is not going well as you said if it's through mate Halaand's performance is not going well as last season, which is also due to the absence of kelvin De bryune, because when we said the key player who always assists Halaand in svoring
City played with the best squad last season. There's no even need to mention what was line up used by city but the key owned by de bruyne and rodri at this moment. The red card has forced rodri to go out for around three matches due to the serious foul. Haaland needs someone who can assist him.
Haaland can do nothing if there would be no player to supply him the ball but haaland is still having ambition to make a better result compared with the previous season. Haaland is a typical striker who was relying with one tap game play.
You can imagine if there was no good attacking midfielder who can supply him the ball. it makes haaland being useless caused by he needs someone to give him the ball and then he can one tap it into the back of the net.