But isn't it the job of a coach to keep an athlete focused?
Initially. But once they get a taste for competition and hard training, to keep athletes healthy for years it is as much a coach's job to keep these eager minds in check. Cerutty did this by encouraging copious amounts of reading and training in natural elements and avoiding the track. The Kenyans follow similar advice, in the sense most of their running is relaxed -competitive but friendly- done in natural surroundings and schooling is never neglected. Natural surroundings means thinking about the path in front of you, the trees, the insects, not tripping over roots, et cetera and not your pace per kilometer. Reading is a clever way to give an active mind something to do when rest and recovery are the only things left to do. So much can be accomplished while seemingly distracted from the task at hand. I am reminded of an ancient Chinese fable:
A young man was accepted into the Shaolin school. He showed up to his first lesson excited to learn.
The old monk led the young man to a raised pool and told him to slap the water.
When the young man came back to class the next day, the monk told him to go to the pool and slap the water. Day after day, this was the only task he was given.
After 12 months, the young man became so frustrated that he broke his instruction and went to the monk who was eating breakfast. The young man demanded a lesson, slamming his hand down on the heavy wooden breakfast table, which immediately broke in half.
Whether competitive or not, thoughts will cross your mind that have nothing to do with winning, and those hours need filling. Keep your eye off the ball, or eye the space around the ball, or don't think about either perhaps. Makes the running part sound easy.