Kelvin De Bruyne was ruled out for lengthy games due to the critical injuries he obtained in the early starts of the season and that have left the Belgium international behind though he has finally returned and have become one of the key project for Pep Guardiola in Manchester City.
I believe he will start in the next game because of how well he played when he came on against Newcastle.
He was made a reserve before not that he played badly but this is a form of caution from Pep because he does not want to overwork him from the start especially since he has just recovered from injury so he will definitely be very guarded because De Bruyne is one of Manchester City very good assets in their midfield so it is quite natural that in the end before in the last 2 match he always played from the bench.
IMO Its only a matter of time because we will be able to see him play in full from the starting lineup bcause indeed his position at Manchester City will never be replaced at this time and that can happen if Pep is really sure that De Bruyne is ready to be played in full and can be strong from the onslaught so as not to get injured for a long time again.