Sasuke doesn't need to use the speed for very long.

As I said in the Naruto vs Rock Lee fight, that match lasted about 2 seconds before Lee used his Konoha Senpuu and knocked Naruto out. And he was still wearing his weights when he did that.

Regardless of whether or not Sasuke would try to kill Naruto, at that point, I don't think Naruto would have won. Sasuke doesn't need a solid defense if his offense is that far out of Naruto's league.



Every fight that Naruto has won is because his opponent was not willing to kill him quickly.

His fight with Haku would have ended very quickly indeed if Haku just threw a needle at Naruto's heart or head.

His fight with Neji would have ended pretty quickly if Neji just tried to kill him instead of humiliating him by disabling his tenketsu. Remember, a blow to the heart with jyuuken is lethal regardless of how tough Naruto is. We already know that Naruto's heart is vulnerable (from the Kabuto fight).

His fight with Gaara would have ended quickly if Gaara wasn't just playing around with his sand shurikens.

His fights with Tsunade don't bear talking about.

His fight with Kabuto would have ended quickly if Kabuto just pulled out the knife in the very beginning, or hadn't been trying to convince him to run away.