Rodri is the most effective player for Manchester City and I know even Pep Guardiola knew this about Rodri and his effete in Manchester City. Rodri is out for 8-9 months which is a long time for this player and he also needs some time to start training with the team and get back to good form to play for Manchester City again.
You can easily understand how effective is Rodri for Manchester City if you check the data and compare it with the time when he was playing for his team.
Rodri is a very important player for Manchester City squad. And I would say the three most important players for City at the moment are Rodri, De Bruyne and Haaland. Rodri and De Bruyne played the most important role in keeping City's midfield stable. So I wouldn't be surprised if Manchester City's midfield is a bit unstable due to Rodri's injury. However, Manchester City's midfield has talented players like Silva, De Bruyne and Gundogan. City will certainly miss Rodri though. At the same time, De Bruyne's fitness is a little weak. He has suffered several injuries in the last season. He is also facing injuries this season. So I don't think De Bruyne can stay with the City squad consistently. Keeping Manchester City's midfield stable will not be easy at all if De Bruyne and Rodri are not with the squad.