Nadal captured this best when he remarked just last month that Djokovic had reached a higher level than Federer.
Thiem, who made the fourth round at the Open past year, was confident he would be 100 per cent by his first match.
Serena Williams, Svetlana Kuznetsova and Victoria Azarenka will be missing from the women's.
To predict a victor of either of the singles titles is hard.
Last season gave renewed hope that Dimitrov might still blossom into the Grand Slam champion he seemed set to become as an extravagantly-talented junior.
"The boys are young and one of them was watching me at the Hopman Cup last week and he said: 'I can do what Papa can, I can play tennis too'". This leaves several top players who all could potentially lift the trophy at the end of the fortnight, with it being possible to make cases for any of Muguruza, Halep or Pliskova.
AUCKLAND: Top-seeded and defending champion Jack Sock bowed out of the ATP Tour's ASB Classic in its second round Wednesday, beaten 6-3, 6-3 by unseeded German Peter Gojowczyk on a bad day for American players.
Djokovic had a contrasting 2017, starting at No. 2 but losing in a second-round upset at the Australian Open and not playing again after Wimbledon. At the US Open and World Tour Finals, last year's Australian Open champion Federer appeared worn out, losing to Del Potro and Goffin in the latter stages. And of course there are all the health concerns, like with Nadal's knees and Djokovic's elbow. With so much time off from the sport, it's going to be interesting to see just how much rust there is for Djokovic.
Meanwhile, last year's semi-finalist and current ATP Finals champion Dimitrov has No. 17 seed Nick Kyrgios, Canadian teen Denis Shapovalov, or former runner-up Jo-Wilfried Tsonga all as potential fourth round opponents. Martina Navratilova, who, like Court, is a member of the International Tennis Hall of Fame, is one of the more prominent figures who have called for a change. While it may be pushing it a bit to describe the world number eight as an outsider for the title, her age and lack of experience at the Australian Open mean she should not be seen as a favourite for the title.
"The most important thing is to feel the conditions, to get comfortable", he said.
This year's Australian Open was shaping up to be one of the most underwhelming editions, with numerous top-ranked players being forced to withdraw from the tournament because of injury. Bencic, who came back from left wrist surgery previous year is on a 15-match winning streak and showed stunning form in the Hopman Cup last week.
Wawrinka's own attempts to prove his fitness have not proved so fruitful.
Should Djokovic come through that, he could face France's former world No 6 Gael Monfils, who enters the Australian Open as the recently-crowned Qatar Open champion - a tournament Djokovic has twice won but opted to miss this year to continue his recovery.