In the first of our Greatest Of All Time semi-finals the two men with arguably the strongest claim to the title go head-to-head.
Top seed Roger Federer takes on Australian legend Rod Laver for a place in the title match.
Grand Slam titles: 16
Australian Open winner (2004, 2006, 2007, 2010)
French Open winner (2009)
Wimbledon winner (2003, 2004, 2005, 2006, 2007, 2009)
US Open winner (2004, 2005, 2006, 2007, 2008)
Grand Slam titles: 11
Australian Open winner (1960, 1962, 1969)
French Open winner (1962, 1969)
Wimbledon winner (1961, 1962, 1968, 1969)
US Open winner (1962, 1969)
Simon Reed's verdict
When Laver did his first Grand Slam most of the other big names had turned pro so he was comfortably the best player left around. You can never say a Grand Slam isn't impressive but it meant less than the second one.
Although by the time the second one came around, most of these guys had got older and were beginning to retire. So in many ways that gap worked for him either side.
But he was a heck of a player and a delight to watch. It was great watching him play, he did elevate men's tennis to a new level. But Federer has done that also.
If you imagine Laver playing Federer, Federer wins every time, that's the problem with this one; you can't get that out of your head.
On grass Federer would have been too good. I would see him winning that with at least one break of serve and possibly two, definitely comfortably.
The other two surfaces would be tougher. I think we underestimate Federer on clay because of Rafael Nadal. I think Nadal has been the best ever clay court player and if it hadn't been for Rafa I'm convinced Federer would have won three of four French Opens.
I think he's a very good clay court player and I have Federer winning on all three surfaces.
You have to imagine how Laver would play and there's no doubt he would be very difficult to knock over. He would be even fitter, even stronger and all the court craft he had, the wonderful game and fantastic backhand he had, he wouldn't have been easy.
But Federer's record is better than Laver's; he has won more Slams and he has elevated men's tennis in the way that Laver did. He is the better all round player.
Federer wins: 6-3 (grass) 7-5 (clay) 6-3 (hard)
Who do you think would win?