Galen is probably the most talented US distance runner around right now. Unfortunately, he has never shown that he will be able to sprint well at the end of a 10k and will therefore likely never medal, much less win, in a major championship race. If he upped to the marathon now, he might actually be able to maximize his potential in that distance and win a major race, but at this rate, by the time he starts marathoning, he'll be too old to ever reach his full potential. I understand that Salazar is thinking long term, but at some point, he's got to realize that no matter how fast Galen runs, he will still get absolutely smoked in the last lap of a 10k. The marathon is his only chance to really claim absolute glory, but he's not getting any younger and that chance will be gone soon.