[4:133] If He will, He can remove you, O people, and bring others, surely God is ever able to do that.
One Who has no need of another in all sempiternity has no need for him in endless eternity. It is said He has no need for anyone, while the servant is not able to do without Him for even a single breath.
It is said there is no limit to the things which are decreed: if it were not ʿAmr, than it would be Zayd. If it were not a servant, it would be servants. The only one for whom there is no substitute or replacement is the One, the Unique.