Originally Posted by
Impossibility
The only attack Sasuke possesses that would likely be effective against Gaara is his Genjutsu. Amaterasu, Kirin, Susanoo are not likely to particularly effective against Gaara. Amaterasu is too slow-burning to be of particular concern, Kirin requires prep time that would likely allow Gaara to take control of massive amounts of sand in order to defend himself. Gaara would likely overwhelm Susanoo by simply grinding away at it with his sand until Sasuke is unable to keep it materialised. The only way I see a victory for Sasuke is if he immediately closes the distance and traps Gaara within his Genjutsu before Gaara' s sand comes to the defence, unlikely if Gaara and Sasuke have any real distance at the start of the fight or Gaara is prepared to immediately take the defensive; something that is his natural inclination. However, if Gaara is a significant distance from Sasuke at the commencement of the battle, or manages to establish his defence, the battle significantly favours Gaara from start to end. The longer the battle, the more improbable any sort of victory for Sasuke becomes.