The Norwegian striker has scored 10 goals in his first six Premier League games since his £51 million ($58 million) move from Borussia Dortmund this summer.
"All the players who come here were brought here by the club to make us better, that makes sense," said Guardiola ahead of Tuesday's opening group game away to Sevilla.
"If we rely on Erling's shoulders, we will not win the Champions League."
City reached the semi-finals of last season's competition before an astonishing comeback from Real Madrid cost them a shot at winning their first European title.
The Premier League champions have brought in England midfielder Kalvin Phillips (26), Argentine striker Julian Alvarez (22) and defenders Manuel Akanji (27) and Sergio Gomez (22) to strengthen their squad.
However the capture of Haaland was the main deal, and one that Guardiola hopes can inspire City to the trophy in Istanbul next June.
"Hopefully, we can do it," said Guardiola.
"He came here because we convinced him. We didn't have strikers and he felt he could play with us.
"I understand completely why everyone is talking about Erling but I have six new players and I want them to settle as quickly as possible.
"We won't win just because of Erling but he has a special talent, and he can help us solve problems, definitely. But if we don't play well, we will not win."
City will be without defensive pair Kyle Walker and John Stones against Sevilla.
Walker limped off towards the end of Saturday's 1-1 draw with Aston Villa, while Stones also picked up a minor knock.
"[They are] injured. John is not much. Kyle is not much too, but I don't know if he will be ready for Saturday, or Dortmund or Wolves before the international break," said Guardiola.
