Asking a guy to "tough" his way through a pulled hamstring is absolutely retarded. A pulled hamstring isn't a sprained ankle you don't just work through it. If he pushes it too hard he can go from a partial tear to a full tear and be out all year. He needs a good 1-2 weeks of rest from running in order to heal it fully, longer is the pull is serious. Few things are more damaging to the career of a speed athlete as recurring hamstring pulls are.