What Causes Numbness In Foot?

Hello, I have experienced for the past 2 weeks after approx 20-40 mins into a competitive game of football my foot going completely numb rising to my calf on my left side. I take creatine for gym work outs but did not take any before my most recent football match but the foot still went completely numb. I loosened my boots and shin pads but this did not make any difference.