The pair have impressed since stepping in to cover senior absentees.
Ahead of today's trip to Manchester United, Guardiola reflected: “It’s surprised even me how connected they are and how they help each other. It’s been tough games.
“Brighton was a debut for Max and then of course Exeter was a little bit different for the result and then Newcastle away. They were brilliant.
“At the beginning of the season, if you tell me at this important part of the season that this would be the back four I’d say ‘are you sure?’
“But the season is never flat or on the same path, you have to handle it. Nico’s already played many times there; Nathan can play there.
“I’m happy Rayan Ait-Nouri is back, he has incredible special quality not just in the final third but in the build up to help us a lot.
“Khusanov, when he has played this season, he was injured against Arsenal and was out many times, he’s important for us. He’s behaved really well.”
He added, “I knew Max from training for two years with us.
“He still has a big margin to improve but in general comparing not sessions because we don’t have them but from video, how quick he got the things is really, really good.”