TENNIS: Roger Federer would end the argument over who is the greatest player of all-time by beating Rafael Nadal in tonight's Australian Open final.

That's the opinion of former world No.1 Andy Roddick, who considers the match "definitely the most important match in Australian Open history on the men's side and potentially in grand slam history."

The Swiss superstar is chasing an unprecedented 18th grand slam title, while Nadal has the chance to move within two of the all-time leading major winner Federer.

But not only would a Federer win at 35 move him four grand slams clear of Nadal and Pete Sampras, it would also be an emphatic statement in the face of his poor head-to-head record against the Spaniard, Roddick says.

"I do think if Roger wins it kind of puts him too much space between him and Rafa, Novak (Djokovic) ... that's a lot of ground to make up," Roddick told foxsports.com.au via the online social marketplace Charly.

"But I also think it affects it on a legacy perspective past just the numbers.

"I've talked to very, very big people in tennis, big former champions who still say Rafa has a claim to the best ever, just based on their head-to-head match-up.

"So I really think if Roger wins this it's an exclamation point saying 'I beat Rafa in a grand slam final'. He's done it before but it would really put some emphasis on the win and 'I have 18' - it's four clear of the field at this point.

Legends divided over FedalLegends divided over Fedal1:02

"I think it's as simple as if Roger wins this match, as it stands currently, he's the best player of all-time and I'm not sure people would be able to argue that anymore."

Roddick, though, suggested it would be tough for Federer to turn the tables on his old foe, and pointed out there was plenty at stake for Nadal.

"All of a sudden, if he (Rafa) sneaks a win here, and he is always in with a realistic shot of winning that French Open ... all of a sudden it (Nadal catching Federer's record) becomes a realistic conversation again," Roddick said.

"We kind of all had left Rafa - at least his better days of tennis - for dead a little bit and I'm certainly guilty of that."

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