An Australian Open final between Roger Federer and Rafael Nadal could be the most important match in grand slam history, according to Andy Roddick.
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The two greats remain on track to reach the decider at Melbourne Park, with the draw opening up following the shock exits of Andy Murray and Novak Djokovic.
At 35, Federer is a record 17-time grand slam champion, while 30-year-old Nadal is three adrift.
Roddick, set to be inducted into the International Tennis Hall of Fame, said that could make the final the biggest ever.
"If you think about the historical significance of what that match would look like, one at 14 slams, one at 17 slams," he said on Tuesday.
"Rafa wins, it's 15-17, and the French Open is around the corner, it's back on. It's literally game on for the most slams ever. If Roger wins, it's 18-14. I don't know that that divide gets made up.
"If that happens, it has to be the most important match in Australian Open history and possibly grand slam history."
In the women's draw, sisters Serena and Venus Williams could meet in another dream final.
The fast courts in Melbourne have drawn attention this year, with Djokovic and Murray outdone by aggressive opponents.
Roddick feels the speed could be an advantage for Federer, saying: "I'm sure Roger's not disappointed in the way the courts were playing when he got here ahead of this tournament.
"But like every tennis fan, which is the role I play now, who wouldn't want to see the Williams sisters? Who wouldn't want to see a matchup between Roger and Rafa with history on the line?"