I haven't seen the animated version, but to my understanding, Naruto simply got owned. From beginning to end, Sasuke made him look like a fool that fight. Everything naruto pulled that fight, was pure BS, and Sasuke must've decided that he's not taking shit.

Actually, the fight was evenly matched, but during the chase after Sasuke, the 4 sound guys taught him how to activate his cursed seal to stage 2 and that if he stays in that stage for too long it will eventually take over him.

Sasuke turns into stage 2 at the end and barely defeated Naruto during his nine-tails berserk form. Naruto ended up making a big scratch on Sasuke's forehead protector and I forget where I heard this, but someone said Sasuke would've died if he didn't have the foreheard protector on.

To sum it all up, Sasuke's stage 2 was just barely enough to beat Naruto. Maybe he got a lucky hit on Naruto while Naruto only got Sasuke's forehead protector.

Sasuke turns super saiyan and matches up to Naruto's power, but in the end Sasuke wins.