Novak Djokovic captured his record seventh Australian Open title on Sunday, claiming his 15th Grand Slam crown to surpass Pete Sampras for third place on the all-time list.
If the world No. 1 dethrones rival Rafael Nadal and wins his second Roland Garros championship in June, he will complete the Nole Slam and join Rod Laver as just the second man to hold all four majors simultaneously twice in a career.
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Sampras says one record will not be matched: Laver's two calendar-year Grand Slams.
The Aussie legend won the Grand Slam in 1962 as an amateur and swept the Slam again seven years later as a pro.
Speaking to the International Tennis Hall of Fame in celebration of the 50th anniversary of Laver's Slam, Sampras said the Aussie's record is untouchable.
"He's the most humble champion I've ever been around," Sampras said of Laver. "His records are never going to be touched. Those two Grand Slams will never happen."
Only five players in history have won the elusive calender-year Grand Slam: Don Budge, Maureen Connolly, Rod Laver, Margaret Court and Steffi Graf.
The left-handed Laver is the only player, male or female, to win the Grand Slam twice.
Laver himself said the key to his Grand Slam success was between the ears.
"I think concentration is probably the most important part of the game when you really boil it down," Laver said.
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