I haven't read all the bios but I have read these three: Agassi, Seles, and Courier disliked him and said he did nothing for their game. Agassi and Seles said he actually regressed their game. Agassi's career took a massive upswing when he finally got Brad Gilbert as a coach. Seles said NB made her change her two-hander for a one-hander on her groundstrokes, which caused her game to slip and when she went back to her two hander he kicked her out of school. When you say he "coached" 10 number 1's, it doesn't mean he was coaching them when they were number one. He had the largest group of talent in the world at his academy. Many later became number one.