In the NFL, you have a short shelf life. As a running back, if you're the first pick, and you're NFL life expectancy is only 3. 5-6 years, your first big contract might not come until three years in - well, you might never get there. They need to get those signing bonuses up front because nothing is guaranteed.
On the outside one is a star. But in reality, one is completely alone, doubting everything. To experience this loneliness of soul is the hardest thing in the world.