theory is trying to figure out things when you aren't doing them... Eventually, you apply theory in your playing...
Let's say someone tells you how to play 9 chords (adding the note that comes next to the root in the scale) you know the theory behind those chords, but you still have to learn how to finger them... I think that you can play great without learning theory, but along the way, you have to pick some up to improve your playing, it's like you have two empty bottles, and you can't fill one up without having the other one up to a certain level...
Jaco Pastorius, best bass player on earth, didn't know a thing about theory, but he had to learn some, and eventually mastered a lot of concepts, because he felt like his potential was held by his lack of knowledge...