If soccer players want to run quickly, then they need to be producing a lot of force against the ground. There are two ways to do this; firstly, we can produce this force via our muscles when our foot is on the floor, or, secondly, we can have our foot moving at a very high speed once it hits the floor. For elite sprinters, it is, of course, a combination of the two. So, ideally, you want to have a large range of motion in which to accelerate the foot towards to ground (requiring good front side mechanics); you want to be able to accelerate the foot downwards (requiring good hip extensor strength); you want to contact the ground in the optimal position (requiring good sprint mechanics), you want to be able to absorb and reuse much of the force you apply (requiring good foot and ankle stiffness), and you want to be able to produce force quickly (requiring an optimal level of strength and power).
We all saw Tim Howard destrominate at the World Cup in Brazil. Against Belgium he was a man possessed and kept the USA in the game with some breathtaking saves. He was moving like a cat. Guess what, Tim Howard follows the Paleo Diet.