Here are the reasons why: 1. Federer has a bigger toolbox than mcenroe but mcenroe has a different set of tools than federer. There has to be something in that toolbox fed can use to beat nadal. 2. He is gonna have to start doing something different to beat nadal. The sooner he comes to realize it the better for himself. 3. As federer becomes a father the relaxed company with John and contrasting personalities will be refreshing for both of them. 4. Mcenroe had a doggedness in his playing style and willingness to try things that could inspire Fed. From Macs perspective: 1. his body is not gonna stand up for much longer on the seniors tour. Coaching fed will be a nice replacement for that. 2. He can team with fed to win the singles french open he never won himself.