Sasuke can't do sh*t against Nagato Soul Dragon.Without summoning the Mezo, he isn't using it. Now if we are being too picky, then it's the one who originally awakens the Rinnegan that has mastery over the Mazo, including the control. He simply summons it himself or takes its control. It's that simple. His CT works without a core, his BT was much much superior, and so was his Petra Path.
What is your point anyway?
That's my point.