Consider he might be the 1000th coach asking Nadal to throw a tennis ball as serve advice, I honestly don't see where his credit is. And Nadal probably had his serve compared with all top servers on tour. I think some of these coaches need to understand that pretty much everyone nowadays has the technology to do that right at the comfort of their own home.
The key is really where you can provide the "insight" as to how to DO it. Everyone has seen Federer's forehand and there are tons of video analysis. Where's your federer forehand?