I'd call it a major rebuild. And certainly the biggest test of his credentials to date, by a mile.
Four full backs over the age of 30. A defence who haven't been drilled defensively for three years. An injury prone (to the point of being unreliable) captain. A once star of the team, the lynchpin of every passing move, who is now well past his best. A couple of okay tricky wingers with pace but for me won't be anywhere near good enough for what Guardiola would want (Sterling and Navas). Two attacking players that do nothing defensively (Silva and de Bruyne).
That leaves Guardiola with Kun, Hart and Fernandinho that don't need any working on or replacing. I think Guardiola will like Delph too but he really needs to work on retaining the ball better.
Everyone else in our entire squad needs to improve beyond belief, need to get used to working a fucking damn sight harder, need to get fitter or need to change their ways or none of them will still be here in three years time.