Pep Guardiola has been rotating his Manchester City centre-backs this season because they can't handle playing every three days.
John Stones is currently out injured with a hamstring injury, while Aymeric Laporte has only recently returned to the side after surgery in the summer. Nathan Ake and Ruben Dias have also had to battle injury issues and Guardiola believes rotation is the only way to keep them fit.
Manuel Akanji has hit the ground running since his £15million move from Borussia Dortmund but there has been plenty of rotation elsewhere in defence, with six different defensive line-ups picked in the last six games. Guardiola insists he would like to have a settled pairing to rely upon, but is making changes to ensure the fitness of his defenders this season.
