Belgium global De Bruyne, who has been instrumental to City's success this season, suffered the injury after a collision with Palace's Jason Puncheon in stoppage time at Selhurst Park and left the pitch on a stretcher, with his right leg in a brace.
"He's injured in the terms hopefully it will only be one or two months", he said.
"I don't know", the Catalan said when asked.
"Kevin, we will see tomorrow what he has; whether it's just a kick or something else. But I don't know what happens in the future".
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On only the second occasion this season that City have dropped points in the Premier League, they were even fortunate to avoid defeat to opponents they beat 5-0 in September after Luka Milivojevic missed a late penalty.
The penalty incident itself was a controversial one, with the initial contact on Wilfried Zaha by Raheem Sterling outside the box, before the former appeared to dive in the box, but referee Jon Moss awarded the spot kick.
"Maybe [it was penalty] - I didn't see it really well", he sad. "We have to protect players".
"They have very good players so as a defensive unit you have to be concentrated for 90 minutes".
"We've got the players in the dressing room to go forward - and it's only a matter of time now".
Football fans on Twitter were particularly unhappy with Puncheon after the tackle, with one user calling it a "leg breaking attempt".