Originally posted by: Mongoose
Well, of course no one knows for sure, but I'd think fast taijutsu would at least make the Sharingan less useful. Consider: the Sharingan's main power, outside of Itachi's strange (and frankly somewhat idiotic) you're-in-my-world thing, is to predict and counter opponent techniques. However, the faster the technique, the harder it is to counter just by using the Sharingan, because the user has to first recognize and then act, and unlike the other disciplines of Naruto-anime ninjitsu, taijutsu has no seals or anything to give you more time. The Sharingan user still has to take a few nanoseconds to identify the move and then act to counter, so in essence they have to be
faster than the attacker to be effective. The Sharingan also seems to tire any user out after continued strain, so continued quick taijutsu could theoretically wear the user down. Assuming, of course, that the attacker isn't dead before the Sharingan user starts to tire, since they have to counter anything the Sharingan user throws out in response...