Although I actually hope that all this is just you guys nitpicking and it actually is the M.S, I think it is a much weaker form of it, and the most it could do against Itachi would probably counter-act his M.S.

However, if it IS actually the one and only mangekyou sharingan, its side-effects will most-likely be MUCH worse to Kakashi than it is to Itachi, something like using it for more than five minutes will result in permanent blindness.