Three-time Australian Open champion Novak Djokovic said it is the tournament's loss that world number four Rafael Nadal is missing in Melbourne.
Djokovic got past Nadal in a five-hour, five-set epic final at Melbourne Park in 2012, and the Serb rued the fact a rematch was off the cards this year, due to the Spaniard picking up a virus.
"It is definitely a loss for the tournament, for tennis, for sport in general not to have Rafa playing... it's been, what, seven months since he's played his last official match," Djokovic said on Saturday.
"I know him really well. We grew up together in a way. He's a year older than me. So I know that he's a great competitor, somebody that never gives up, fights till the last moment. And he loves this sport.
"I'm sure if he felt he was ready enough to play this tournament, best-of-five (sets) in the Australian summer that can be brutal and difficult to play, then he would (have) come. He probably felt he needs more time to recover. I wish him a speedy recovery."
On the issue of a tightening of time restraints between points, which has been closely monitored by the ATP in the lead-up events to Melbourne, Djokovic said he would adhere to any advice from tournament referees.
"I guess Nadal and myself, we're right up there mentioned in that topic as the players who would be always in danger of the time violation because of the time we are taking between the points," he said.
"It is the way it is. I don't complain. I cannot have any complaints when I take more than 20 seconds between the points.
"If the chair umpire comes to me and said, 'listen, you should be a little bit more careful about it'. If I do it again, he gives me warning, I can't complain about it. It's within the rules and I will respect it."
Djokovic takes on France's Paul-Henri Mathieu in the first round, with the former leading the head-to-head record 4-1.