Until Sunday, Haaland had started in every Premier League game for City this season, scoring a league-high 14 goals.
The 23-year-old has been struggling with a foot injury, withdrawing from the Norway squad during the recent international break to return to Manchester for treatment.
However, City were forced to do without Haaland, starting forward Julián Álvarez in his place up front.
When asked about Haaland's injury before the match, Guardiola told Sky Sports: "[It is] a bone stress reaction in his foot. After the last game against Aston Villa he felt like this and he can't play."
Guardiola did not say how long he expected Haaland to be ruled out, adding the club would monitor the situation "day-by-day."
Information from Reuters contributed to this report