Gundogan's last season was his best ever at the club, not just because of the treble but because of his overall performance level.
It's easy to forget then that before that season, Gundogan was very rarely a nailed on starter at City. During the time of Silva, De Bruyne and Fernandinho, he was seen as a very good backup. His first notable spell was when he had that great run of scoring in 2021 during our brilliant winning run, but not long after he found himself then behind a midfield trio of Rodri, De Bruyne and Bernardo.
Even the Villa game in 2022 where he got the two goals, he was coming off the bench and the week before at West Ham, he didn't start that either. He actually expressed in interviews how disappointed he was not to start in either game.
Obviously his heroics in recent times have seen him secure legendary status and rightfully so, but I don't see him as being completely irreplaceable - no player is.