In the best-case scenario, De Bruyne will miss the matches against Southampton, Shakhtar Donetsk, United, West Ham United and Lyons before...
Then comes the derby against Manchester United next weekend before the global break.
Although De Bruyne, whose wife gave birth to their second child on Wednesday, does not require an operation, he will fly to Barcelona to see specialist Dr Ramon Cagut.
The 27-year-old has already missed two months of the season after damaging ligaments in his right knee during training in August. Asked if he was anxious about the injury, Guardiola said, "I don't know right now".
"We don't know if it's nothing or if it's something serious". He understands the way we want to play.
"He knows the desire we want for all young players".
"Kevin was already out two and a half months, and we are sad for him. He knew that in the beginning and he made a decision to stay".
Diaz's goals against Fulham were his first for the club and his contract situation has sparked reported interest from Real Madrid. Their game was postponed this week following the death of Leicester's owner and four other people in a helicopter crash on Saturday.
"Today again he was involved with everything offensively and defensively, so hopefully what happened in the last minutes is not serious".