But he's right. Unless Sane, Sterling, Navas, De Bruyne, Silva, Nolito and Nasri are all injured or severely out of form, Celina won't get regular games, Pep or no Pep.
I think his biggest problem might be that he's not the kind of winger Pep likes - he's not the very fast, beats players 1v1 a lot type.
It would have been good to see him as back up to Sané until January if Navas goes though.
Sterling/Nolito --- Aguero/Iheanacho --- Sané/Celina.
And Sterling could always come across to cover if it was a particularly big game of if Celina wasn't up to it.