Check the "tempo runs-useless" thread.
I gave the program in 2011-2012 to the teacher of Geoffrey, Charles Ngeno, when Kirui ran 26'55" in 10000m. After Abel Kirui won Chicago in 2016, Geoffrey Kirui started to train with me directly, coming from Keringet to Iten several time, and I went from Iten to Keringet many times. During this period, Piet continued to take care of Geoffrey, following him when we were not together, according to my plan. This collaboration lasted till World Championships, including the victory in Boston 2017, when in Boston I clearly said, during an interview, that Geoffrey was one of the best talents for marathon, but, because his "low mileage" (160 km per week), NEVER could reach his potential (something that clearly happened)