Now that I've seen 82, I've just gotta say-

Gai doesn't stand a chance against Itachi. Itachi is just too fast. Not even Kakashi could follow his movements, and he has a sharingan. The idea that Gai could even
put up a good fight against Itachi assumes that Itachi needs to use his sharingan to beat him. But the sharingan isn't Itachi's only strength.