As we watch them in the final stages of their incredible careers, it's hard not to wonder about the next generation of talented players.
By next generation, I mean those born in the 1990s, when Federer and Williams were being talked about as possible future stars.
Some, like Jerzy Janowicz, have already made a splash. Others, such as Grigor Dimitrov, are working to live up to the hype.
Then there are those like Simona Halep, who is ranked No. 23. Halep, 22, has quietly won three WTA titles this year.
These young, talented players are inching toward stardom. But just how close are they to becoming bona fide stars?
If we simply consider ranking, No. 11 Kei Nishikori is on the fast track to star status.
But rank is just one element of stardom. Do they have the moxie to match their games? Are they appealing to fans? Can they capture our attention and hold it?
Many are labeled "budding stars." Just how close are they to sustaining stardom?