Rich James IMO has written a  good sensible article  'Recalling Greats'

http://www.tennisweek.com/news/fullstory.sps?inewsid=6640743

He is spot on with the backhand and volley of Federer. A good volleyer want come in on the back hand.  Also look at the return of serve, blocked back, east pickings for the volleyer. IMO Connors and Mac at the US Open would have got into Federer's mind , especially after seeing him cry and break his racket. There is a  fuse ready to be lit in Federer's head. Look at the US Open when he complained about the slowness of  Del Potro.

Mac and Connors for me at the US Open, ( Even the ice man Borg could never win there)

This era lacks volleys and variety