My look at things?
Facts are that despite his goalscoring record for us, he didn't stood out for us the way he can and should do because he is that good a player. He even lost his place in the Argentina team and that should never have happened to a player of Aguero's quality. Maybe it became all too easy for him at City. There was not enough competition and everybody at City just loved and adored him. Just putting in the goals would keep him in place.
Pep demands more, much more. The big signal for Aguero should have been the fact that Pep was chasing Aubameyang as this is not a stand-in foreward. It doesn't happen and at that time Pep already started telling Aguero to step up because in that way he will be more important to the team. Despite scoring his goals, his influence within the team is still limited for a player of his standard. Pep keeps challenging him and orders the player to watch another centre foreward on clips or videos (depending which foreward he had to watch I guess). When Aguero was suspended we hardly missed him, and now Pep has put him on the bench. The penny probably hasn't dropped with Aguero or the changes have him mixed up so he needs time. The former will see Aguero getting in to trouble with Pep, the latter and Pep will help him to become an even better player.
The fact Pep is challenging Aguero means that he sees in him a player that has the talent to be great, has the intelligence to understand and has the physics to live up to his demands. If that wasn't the case Aguero would already be in the same situation to the likes of Hart, Yaya and Nasri. It's simply no use putting your energy in someone who isn't willing or able to deliver. With Aguero it seems to be a mentality issue that can still be explained two ways: in a bad way that the player doesn't want to accept what Pep is trying to do, or in a good way that he needs time to change and is working on this. The mentality-issue rose last week when Aguero spoke after he played for Argintina, had a poor game and missed a penalty, declaring he would not be surprised if he was to be overlooked next time. What was that all about. He should have stated he was disgusted with himself but at the same time make a promise he would make up for it next time and expect never to have a game like that ever again in an Argentina shirt.
Maybe the injury-issue played a part with Pep overlooking Aguero for the Barcelona match, but I doubt that. If the player is fit and he can play he should do so. Aguero did play and lasted the full 90 minutes, so he was fit. He didn't travel back with an injury either.
It will be very interesting to see what will happen with Aguero in the next few weeks. Pretty similar to Lewandovski when he came to Bayern. He had a tough time, but eventually lived up to Pep's demands and became an even better foreward than he already was with Dortmund. I hope Aguero gets the picture. Keown recently stated Aguero is our Messi. He is not, but he can be.