Gundogan is certainly a key player in Manchester City's squad. He may not have scored many goals or assists, but Gundogan has been instrumental in keeping the team's overall performance stable. The important thing is that Gundogan has been with the Manchester City squad for a long time. Because of this, if Gundogan suddenly leaves the team, it will be difficult for Guardiola to fill his void. But Guardiola is an experienced coach. He may be able to find a suitable replacement for Gundogan very quickly and stabilize his squad.
Gundogan is a professional footballer, he is known as an attacking midfielder who has high technique, qualified game vision, and impressive goalscoring ability. Now Gundogan is in the spotlight of various media crews regarding his future, his contract will soon be completed on 30 June. So far Gundogan has made a perfect contribution and has helped the team to win the Treble Winner, I think it will be very difficult for Manchester City if he really chooses to leave when his contract expires, and on the other hand, I have not heard from the management showing any signs will extend his contract. I agree with you, Guardiola is a great coach, and I'm sure it won't be too difficult for him to find the right candidate to fill the void. Apart from all that, now I hear rumors that Guardiola is eyeing a player from PSG to become one of the candidates to replace Gundogan, namely Fabian Ruiz, he is currently on Manchester City's radar. But the news is still speculation and I think Guardiola knows what he has to do.