I had a cousin who in the earlier 90's was a state/national champion in cross country his freshman and sophomore seasons in high school. His jr and senior seasons he failed to qualify for the national race and finished out of the top 10 in the state races. When I spoke to him later on I asked him what had happened thinking it may have been due to an injury. He proceeded to tell me that during his first 2 seasons the field was much stronger around him and the other runners were very good and so he/they forced him to be much better. Once that competition was gone most of the field was mediocre at best and he sunk to that level. Physically he was the same but mentally be felt he didn't have to do to much to win and then realized it was to late to do anything about it.