Originally posted by: XanBcoo
He was referring to Mangekyou Sharingan. Now, I have not read the manga, but I was under the impression that Itachi found out about Kakashi's Mangekyou at the same time we did - that is, very recently.

There is no way he could have known Kakashi was the third person nearly 10 years prior. He was referring to someone else, making Kakashi the 4th user.
Um are you stupid? He simply said Kakshi COULD get the mangekyou not that he already had one, if he was saying that, he'd also be implying that Sasuke already had one.