By John Lloyd
BBC commentator and GB Davis Cup captain
For me the greatest clay-courter of all time was Bjorn Borg but Rafael Nadal is up there with the best already - and you've just got to look at his age.
Nadal beat Federer 6-3 4-6 6-3 6-4 in Sunday's final at Roland Garros
He's only 21 and although there may be some young players who will come through to challenge him, looking at it right now he could win another three, four, five titles in Paris.
We underestimate Nadal's talent because Federer is someone who's got every shot in the book and is one of the most flamboyant and creative players that ever lived.
Up against him, Nadal almost looks a bit stiff - he's not. He knows how to play on the clay and his variety is improving all the time, he's going to get better.
But he is so difficult to face because the physical aspect of his play is just immense and he gets more spin off this clay court than anyone else by miles.
I think Nadal played a good, solid match in Sunday's final - he was consistent in all four sets and didn't really have any big dips - but to me he didn't play as well as he did against Novak Djokovic in the semis because he didn't have to.
Federer takes more chances against Nadal than he does other players because he know who's across the net
As for Federer, there has been some incredible brilliance during these two weeks but against Nadal he has to find a way of combining the power and variety he has with picking the right shots to be aggressive.
At the moment he takes more chances against Nadal than he does other players because he knows who's across the net and unfortunately he can't seem to find the right balance.
He ends up making way too many errors and didn't use the sliced backhand in the final until far too late.
His first-serve percentage in the first set-and-a-half was awful - that would have to change to beat Nadal - and he has to come into the net more.
For me he tried to hit too many big groundstrokes from Nadal's territory - four feet behind the baseline - and I just don't think he can do that. He's got to change his game plan if he's going to beat Nadal in Paris.
But Federer's only 25 and has still got three or four more years of peak tennis. He's too good a player not to learn from this.
I thought he was better this year than last - not as much as we had hoped but he can certainly play better.
I can't count him out of beating Nadal in the future, but it's going to take an awfully big effort to beat him over five sets at Roland Garros.