The 10,000 at worlds is in less than 4 weeks. He just raced a fast 5,000m over the weekend which was good to sharpen up a bit and get a good racing effort somewhat close to worlds. If you want him to do a mini taper to try and win the 5000m this weekend he'll have 3 weeks before the 10,000 meters final at worlds. When do you expect him to get a hard training cycle in? Right now at 4 weeks from his last week it's the perfect amount of time to build up a good week of mileage this week, get 1.5 weeks of good quality with decent high mileage before getting in a true taper into July 17th to give his best effort in the 10,000m. Not racing the 5000m is a very good decision in my book to be able to have his best performance at worlds.