If we go by the rumours, he's going to replace the entire team. I don't see why he'd replace Fernandinho. He might play him more defensively though. He's getting on a bit, but let's not forget that Pep brought in Xabi Alonso to Bayern aged 32 and he's still playing now.
At the start of the season, I thought we would be in pretty good shape for Pep's arrival, but I think there's quite a bit of work to do. In central defence, we're now at a situation where we've seriously got to decide whether we want to rebuild around a new CB, because Kompany's constant injuries are affecting the team. TBH, the central defence depends entirely on how Pep views the existing CBs. It might be that with his organisation, the existing players will look like world beaters. Obviously with the homegrown issue, there's a big incentive to try and give Denayer a chance next season too.
I thought that the full backs would be good for another season, but Zabaleta and Kolarov are both looking to be struggling to keep up with the demands of the Premier League this season. Clichy and Sagna look like they've got at least another season left yet though, but now would be the time to bring in younger challengers.
Central midfield has looked weak all season. Fernandinho has been the only player that's shone, and while Fernando has done a decent job, he still doesn't look up to the level required for a world class team, especially given the sort of football Pep likes to play. Toure's decent performances have been pretty rare this season and it's probably time to move him on. Delph hasn't looked up to standard so far, but I'd give him a chance with the new manager. And let's face it, he's English, so unless we're buying Barkley or Alli, we're probably not getting rid. Gundogan is the obvious signing, and seems to be a bit of a bargain due to being in the last year of his contract. Pogba too would be incredible, but it's a big ask.
I think we're set for attacking midfielders and wingers, tbh. I think the players we have are good enough, but obviously youngsters like Sane would always be a welcome addition. Pep also used to play Henry and Villa out wide for Barcelona, so I'd expect to see Nacho out there on occasion.
Up front, the emergence of Nacho has been a huge bonus this season and we now have a very good backup to Aguero who's young enough that he doesn't mind being backup. But let's not pretend he's the finished article. Bony seems to have regressed even from his slow start. He never scored many goals for us, but when he first came, I at least thought his build up play was decent. But he looks to be on his way out. The eternal dilemma, of course, is how do you get a striker that's willing to be behind Kun in the pecking order, but good enough to come in when he's injured (which is a lot). I think the answer is that you get someone who can play across a front 3, like Aubemeyang.
Hart
Sagna------Otamendi------Mangala------Clichy
Fernadinho---Gundogan
Aubemeyang------De Bruyne------Sterling
Aguero
New GK
New RB------Kompany------Denayer------New LB
Fernando---Delph
Navas------Silva------Nasri
Ihenacho
To go: Bony, Toure, Zabaleta, Kolarov, Caballero.
Although this depends on the reasons for Zabaleta's lack of form. If it's just rustiness because of injury, then he might be worth keeping around. After all, it was only a couple of seasons ago that he was being suggested as the best RB in the world. TBH, I have a hard time judging any of our defenders individually, when the overall organisation has been so shocking.