Roger Federer says the so-called Big Four in men's tennis — he, Novak Djokovic, Andy Murray and Rafael Nadal — still exists, with one possible notation and an addition.

"Novak deserves like a little star next to his name right now because he's been doing extremely well," Federer said Saturday.

The Australian Open begins Monday with Djokovic set to defend his 2015 crown and aim for title No. 6 at Melbourne Park. Last year, Djokovic won 27 of his 28 matches in Grand Slam tournaments, capturing three majors and finishing runner-up to Stan Wawrinka at the French Open.

That run left Djokovic unquestionably as No. 1, with Murray second, Federer No. 3, Wawrinka ranked fourth and Nadal, after a series of injuries, back to a spot in the top five.

Order restored, says Federer.

"Who's had the most success? The top five guys really, with Stan, you know, Murray, myself, Novak and Rafa," Federer, who plays his first-round match Monday. "Now the rankings are back to more normal again after Rafa's worked his way back up."

Djokovic, in the same half of the draw as Federer, will open his defense against Chung Hyeon of South Korea and, if results go with rankings, could meet No. 7 Kei Nishikori in the quarterfinals and Federer in the semis.

Federer, who has won four Australian titles among his 17 majors, opens against Nikoloz Basilashvili of Georgia, and possibly Alexandr Dolgopolov in the second and No. 27 Grigor Dimitrov in the third.

No 2-ranked Murray will open against Alexander Zverev of Germany and, in the same half of the draw, 2014 champion Wawrinka takes on Dmitry Tursonov.

Nadal, who could meet Wawrinka in the quarterfinals, opens with a tough encounter against fellow Spaniard and 2009 Australian Open semifinalist Fernando Verdasco. Nadal beat Verdasco in an epic five-setter that year and went on to win the title.

"Not a lucky first round, I think, for me. For him either," Nadal said Saturday. "Will be a tough match."

Asked to reflect on the 2009 result, Nadal said: "Obvious that that match gave me the chance to win the only Australian Open that I won. That was an unforgettable memory for me. "

Nadal won three titles last year but it was the first year since 2004 that he hadn't won a major. He was beaten by Djokovic in the Qatar Open final two weeks ago and lavished praise on the Serbian, saying he was virtually unbeatable in that match.

He continued the sentiment on Saturday.

"Novak is playing at (a) better level than the rest of the players now, that's obvious," Nadal said. "The way he's playing, it's difficult to see him losing matches. Just can congratulate him for making that happen. "

Murray says he knows well and has practiced recently with his Tuesday opponent, the 1.98-meter (6-6) Zverev.

"It will be a tough match," Murray said. "He serves well. For a big guy, moves pretty well ... obviously improving all the time."

Murray and his wife, Kim Sears, are expecting their first child in February. On Saturday, he reiterated earlier comments that he would return to London immediately if she went into early labor, even if it was between the semifinal and the Jan. 31 final and it left the tournament without a championship decider.

"For me, my child is more important to me, and my wife is more important to me, than a tennis match," Murray said.