Off contract in June, Bernardo was again outstanding as City won the first-leg 2-0 on Tuesday night.
“Today, again you cannot imagine what a player Bernardo Silva is,” said Guardiola.
“This player will be missed, but hopefully he can stay for many centuries.
“That guy knows what it is to play football and to be a competitor. He knows the rules, absolutely everything.”
On the players who stepped up at St James' Park, Guardiola added: “Rico (Lewis) came up and Rayan (Cherki) came up. Rayan Ait-Nouri came from AFCON.
“Everyone made their contribution. The same as last FA Cup game or against Chelsea and Sunderland and Brighton and I know it’s a pity because the games we played was really good, but we didn’t score But were there.
“The spirit is there. I smell it any every training session.”