It wouldnt be a miracle, sasuke put up a pretty good fight against itachi without having MS at the time
Okay, for the what feels like 500th time.
It has been established quite some time ago in the manga that Itachi let sasuke win to give him his MS abilities.
Itachi was simply a judge, yes you have become strong enough to recieve my powers, or you haven't.
He had, so Itachi let him win even though he could own Sasuke easy.
Itachi could have won straight off with Tsukyomi, theres a reason Itachis illusion wasnt attacking sasuke like kakashi, wearing him out.
It was to teach sasuke, and tell him of madara, who incidentally told sasuke theres no way he would have won if itachi fought seriously, plus zetsu stating itachi wasnt fighting at his best.
Even diseased and blinded, Itachi was doing less well than usual, Itachis been blind for quite some time.
Sasuke is powerful, but he lacks experience, and has only just got MS abilities that stress him a lot, plus he's just been quadrouple tagged by the 4 kages, and now he's been chucked into a fight against the 5th half hour later.
Sasuke is worn out, yes karin has healing blood but its not like a computer game 100% healing potion- you can see from the art sasuke is still tired
Personally tobi is just stress testing sasuke to train him and get him more blind so he will take Itachis eyes.
Also tobi and danzou know each other....
I'm thinking there's a lot more to this than meets the eye (no pun intended)
Tobi might be using Danzou to harvest sharingan eyes or something...like spares...just incase...
Maybe this is all roleplay...I mean...Tobi hasnt KILLED anyone, he's just got them out of the way.
Make sasuke think its a real fight when it isnt.