Buxton struggled right out of the gate. He adjusted rather quickly and has been off the charts good ever since.
The other thing is if you are comparing him to Harper and A-Rod, again to put the hype in perspective. ARods first season he was a .950 OPS bat as an 18 year old and reached AAA. Harper was a .900 OPS bat as an 18 year old and reached AA. Buxton on the other hand was a .790 OPS bat as an 18 year old reaching only Rookie ball. As, far as how that shapes their MLB careers it is fairly meaningless but as far as the hype machine goes it means something. The other thing to keep in mind is coming into this season, Buxton was not even considered the best prospect on his own team, Sano was.