For the win over Tottenham, De Bruyne was substituted after suffering an injury.
Guardiola admitted the extent of De Bruyne's knock is as yet unknown but predicts the midfielder will not be in contention for the midweek trip to United.
"I don't know," he stated. “I didn't speak with him or the doctors.
"It was something muscular, which is normal after injuries and three or four games of a lot of minutes with no preparation.
"Maybe he will miss the four games and the FA Cup Final. I don't know how big the impact is.
"We will see tomorrow but I think for the next game, he will be out."