Originally posted by Mindset
When Naruto headbutted Gaara he was in his bijuu mode and didn't have his ultimate defense.
Actually I've NEVER seen gaara use his sand armor defense thingy besides that 1 fight with lee since he always seems to be hurt by every other attack... And always has facial expressions. The whole fight was just to make gaara look tough. When gaara becomes an actual character that all goes away.
All Lee had to do was take off his weights and gaara wouldn't even be able to see him let alone touch him. If he actually used his weights as weapons like he did in one of the movies he probably would have been able to do enough damage output without the gates as well.