Novak Djokovic bids for an unprecedented third straight Australian Open title from Monday, with growing rival Andy Murray and the great Roger Federer shaping as his biggest challenges.
Argentina's Juan Martin Del Potro is the only man besides Djokovic, Rafael Nadal, Federer and Murray to win a Grand Slam tournament since 2005, but the Serb said there were plenty of others who could threaten their dominance.
"It's probably expected that the three of us, and Nadal of course, would still be main candidates to win all the major titles," Djokovic said.
"But, you know, I wouldn't underestimate Del Potro, (Jo-Wilfried) Tsonga, (David) Ferrer, (Tomas) Berdych, anybody who is in the top 10.
"I'm sure there's new young players coming up like (Bernard) Tomic, (Grigor) Dimitrov, (Milos) Raonic.
"I don't think it's nice for me to predict that us three will be champions of all Grand Slams this year."
However, the odds favour Djokovic who is targeting a third straight Australian title, a feat which has not been achieved in the professional era.
Nadal is not playing due to illness, robbing Melbourne Park of a repeat of last year's epic final, when Djokovic finally tamed the Spaniard at 1:40 am after a record, 5hr 53min final which left him with bleeding toes.
But Djokovic will face a stiff challenge from the newly assertive Murray, fresh from his first Grand Slam win and keen to avenge his final and semi-final defeats to Djokovic in Melbourne in 2011 and 2012.
Also pressing hard will be Federer, holder of an unmatched 17 Grand Slams and still hungry for more even though, at the age of 31, he is conceding six years to his younger rivals.
Murray, 25, said the Grand Slam breakthrough at Flushing Meadows in 2012 eased the pressure and set him up perfectly to build on the best year of his career.
"Not just Grand Slams. You know, I kind of maybe always felt like I was having to prove something every time I went on the court because I hadn't won a Slam," he said in Melbourne.
"You know, even when you win a Masters Series, people still asked me always about the Slams. So it's nice just to kind of not have to worry about that any more.
"I think it will help me throughout the rest of the year, as well, on the tour because I just won't be worrying and thinking about the Slams all the time, I can focus on all of the events that I'm entered in."
Murray, the world number three, was thrashed by Djokovic in the 2011 Australian Open decider, and narrowly lost out in their thrilling five-set semi-final last year.
But the Scot then beat Djokovic on his way to London Olympics gold, and again in the US Open final as he became Britain's first male Grand Slam singles winner since Fred Perry in 1936.
Meanwhile four-time winner Federer, keen to extend his long stay at the top of men's tennis, opted out of playing a warm-up tournament. The Swiss has not reached the Melbourne final since his last win in 2010.
But he said it had allowed him to feel fresh and eager for more Grand Slam glory as he prepared for his 53rd straight major.
"I purposely didn't play a lead-up tournament so that I'd be fresh for the beginning, hopefully going deep into the tournament. That's the goal obviously," he said.
"I think it's nice sometimes doing it slightly different than every year the same thing. Otherwise it feels like a deja vu and that's not always a good thing.
David Ferrer, who won the most matches (76) and titles (seven) last year, is the fourth seed and is in good form having claimed a fourth ATP Auckland crown by beating Philipp Kohlschreiber in straight sets Saturday.
In Nadal's absence, he has a chance to climb above the fourth-ranked fellow Spaniard for the first time in his career.