Novak Djokovic says Rafael Nadal "absolutely" remains the claycourt benchmark and chief roadblock standing between the Serb and sporting immortality.
Djokovic will head to Paris in May hoping to become the first man in 47 years to hold all four grand slam singles trophies simultaneously after adding the Australian Open crown to his 2015 Wimbledon and US Open triumphs.
The world No.1 also had the chance in 2012 to join Rod Laver, who completed a calendar-year sweep of the majors in 1969, as the only other man in professional tennis history to achieve the feat.
Nadal denied Djokovic in a controversial final that year that finished on Monday after the Serb was up a service break in the fourth set when the match was suspended because of rain.
Nadal returned the following day to break back, take the title 6-4 6-3 2-6 7-5 and shatter Djokovic's grand slam dreams.
The claycourt colossus has since beaten Djokovic in the 2014 French Open final and 2013 semi-final, when the Serb let slip a 4-2 advantage in the fifth set.
Djokovic gained a semblance of revenge last year, crushing Nadal in straight sets in the quarter-finals, only to stumble in the title decider against Stan Wawrinka.
The loss to Wawrinka remains his only defeat in the past five majors and Djokovic will return to Roland Garros eyeing a non-calendar-year grand slam following his victory over Andy Murray in Sunday's Australian Open final.
Djokovic is undeniably the dominant force in men's tennis and already a hot French Open favourite and Nadal - who turns 30 in June - appears on the decline after failing to win a slam last year for the first time in a decade.
Djokovic, though, insists the Spaniard remains his greatest threat on dirt.
"Absolutely," he told AAP as he basked in the glory of a record sixth success at Melbourne Park.
"You would be disrespectful to everything he has achieved in his career on clay courts if we didn't see him this year - and each year - as the ultimate challenge on clay courts.
"Everybody knows he is the king of clay. He's achieved so much on that surface. He's made history. He's won the French Open nine times.
"So, yeah, it's definitely going to be interesting to see how everything unfolds on that surface.
"But we still have to remember that there are still many more important hardcourt tournaments (beforehand).
"So I started the season in the best possible way and hopefully I'm able to do as well as last season in this period up to the French Open."
Djokovic can also join Nadal, Laver, Roger Federer, Andre Agassi, Roy Emerson, Fred Perry and Don Budge as only the eighth man in history to complete a career grand slam with a title breakthrough in Paris.