I found interesting similarities in the Grand Slam runs between Sampras and Federer as well as Borg and Nadal in terms of their Age vs Slams won!
(Note that have taken 31 yrs as maximum age considering Sampras retired at that age for apples to apples comparison for the 14 slam win rate).
Some important pointers:
1. Pete Sampras had only 3 wins in his last 16 slams.
2. Roger Federer needs only ONE win in his next 15 slams to equal Sampras and just 2 to break the world record.
3. Nadal has more than 35 slams to beat Sampras, and is close to beating Borg’s slam total by age 23
4. Borg had the highest rate of slams by age 23 and played only 3 slams a year. He never played a lot of Aussie opens (except early on in 1974 types ) as he kept losing US Opens . Borg didn’t feel Aussie Open was important unless he won the US Open.
Nadal seems to be slightly behind Borg’s run rate. And Federer’s win rate is next to Borg despite playing way longer schedules. Unbelievable.
Nadal too may burn out like Borg especially because his game is more Physical than Federer’s and the body takes punishment on hard courts. Nadal also won’t be able to maintain the speed and power beyond age 25-26…as the tennis schedules are too long now days. Federer’s game like Sampras suits long term play.
But I feel even if Nadal wins 15 slams and Federer wins the French, they can still be called greatest only of the MODERN era as people forget Rod Laver and Ken Rosewall were banned for more than 44 Slams due to them turning PRO… Rosewall lost peak 11 years of his life. It was Laver and Rosewall’s efforts which led to the Open era in the first place and modern players from Borg to Nadal and Federer have to be thankful for them. Between them, Laver and Rosewall would have won 20+ slams if allowed to play as there was no one close to them. And it isn’t their problem that Hardcourts weren’t provided for Slams, as either would have won for SURE if there was that surface provided. It is for this reason, that historians will ALWAYS place Rod Laver and Ken Rosewall as the Greatest Tennis Players of ALL TIME. To beat them, the minimum no. of slam which Federer or Nadal must win are 20, else there is no comparison for the unfair way in which Laver/Rosewall were prevented for 44 Slams simply because they turned Pro.
For a detailed perspective, please also read the following article: