give me one scenario how Itachi can defeat a dozen km clones without the kyuubi taking naruto's chakra. with each clone able to make more clones, which DON't disperse after being hit (if a naruto clone took the backlash of madara's meteor, and the clones of that clone got hit by susanoo and still survived, i doubt itachi's taijutsu is going to do anything). and those clones able to enter sm. plus, the kyuubi can break naruto out of simple genjutsu, so itachi can't one shot.
naruto is a freaking one man army right now, there's a reason why his clones haven't all being fighting at one spot, and it's because he would be overpowered.
now, to defeat naruto, itachi has to either defeat all his clones and kill the real one, or to somehow guess which one is the real one (an impossible feat by the way, even neji failed with his byakugan), and amaterasu,totsuka sword, or tsukuyomi him. all with his paltry stamina, and none of his attacks are guaranteed to work, he can dodge the first two with his speed and itachi would die of chakra exhaustion trying to break down naruto's will with the kyuubi backing him up, 3 days are not going to be enough.
in short, Naruto is the absolute worst opponent Itachi can fight. worse than Gai vs Kisame or Sasuke vs Deidara.