From a Rafa fan this may seem a strange thing to say, especially as he lost relatively early in the AO this year and hasn't had the best of the recent match-ups with Rafa in the slams.
But he is the one player who can not only beat Rafa when he is on it, but can beat absolutely anyone in history in my opinion, at least on today's courts. He *only* has 6 slams to his name I know, which would put him alongside the Edbergs and Wilanders arguably as a Tier 3 player.
But for me in terms of actual ability, he is a Tier 1 great. I think he will end up with 10+ slams. He won't get close to 17 or 18 and ultimately that will be what he is judged on. But purely as a tennis player on today's courts, I would say he almost has no equal bar Rafa, and that is always a 50:50 match.
LOL. People love to build tiers to place these players in. I tend to think it's all fairly meaningless. You can't compare a serve-and-volleyer with a baseliner. What if you are a terrific serve-and-volleyer who has the good fortune to be born at a time when courts are fast, but the bad fortune to be born into a generation of the 4 or 5 greatest serve-and-volleyers of all time? You would end up sharing all those slams. The numbers water down the apparent greatness of the individuals. I have always argued---and still believe---that Federer has 17 slams because he came along in the perfect window of time when there were no big talents to challenge him. Look at his slam record for the first half dozen of his titles---a half-dozen different names, none of them great. Now, he added to that over the years, but a big chunk of his total was fortuitous timing.
As far as I am concerned, once you get past a certain number of slam titles, whatever that number might be, we should forget talking about tiers and simply put you in the top group. For me, the number would be maybe 6. In my mind, the top group would include not only Rafa and Roger, but Djokovic, Sampras, Laver, Borg, Wilander, Agassi, Connors, McEnroe, Edberg, Lendl, Becker, Emerson, and maybe one or two more. That doesn't even begin to consider other massively talented players who, for one reason or another, never had the chance to prove they belong there---Tilden, Gonzalez, and the like. I think Courier was very gifted, but was born into the wrong generation. So was Chang.
But people love to form categories and argue about who should be in which. LOL.