Matuidi being favoured for how he readily made fit he is characterisim wise and his running capabiliies is one thing (basically this Juve's Allan for Sarri). But if it was just about Matuidi being prefered over him, then Rabiot would gotten a sub appearance as vice Khedira or Pjanic, but he hasnt. Can, Bentancur, and now the previously injured all year Ramsey is getting subs and a start. That tells me it has little to do with just Matuidi being preferred (thats a challenge for a later day), Rabiot not getting a single minute on the pitch still has to be bigger then that.
So defenitely something is wrong in terms of how prepared he is to play. Sometimes we have to take things at face value, the coach is litterally telling us he isnt ready and in good shape. Whatever he is doing in training is not convincing them. But still early days. Needs to get going, because no one will wait around to give him chance unless he is fully prepared for it.