Novak Djokovic provided a concerning update after scraping through against Alexei Popyrin late on Wednesday.
Djokovic, 36, saved four set points to take the third set against a determined Popyrin, going on to win the match by three sets to one in the second round of the Australian Open.
But the Serb was visibly affected by a wrist issue that has hampered him for some weeks, while he appeared to be struggling with a cold with his form dipping to as low as fans have seen it for a while.
Going into the tournament, the world No 1 admitted his participation was in doubt after suffering a shock straight sets defeat to hometown hero Alex de Minaur in the United Cup beforehand.
And when asked about those concerns by Eurosport, Djokovic admitted that he is not at 100 per cent.
Novak Djokovic has raised concerns over his fitness after his second round win in the Australian Open
The world No 1 beat Alexei Popyrin in four sets as he survived scare at the end of the third set
Djokovic had been dealing with a wrist injury and was unsure of its severity going into event
‘I don’t really want to get into the details on how I feel, but I’m definitely not playing and not feeling my best,’ he said.
‘But I have been in this kind of situation before many times and hopefully I build as the tournament progresses.
‘Hopefully things will go in a positive direction.’
Djokovic won 6-3, 4-6, 7-6, 6-3 following a gruelling clash in Melbourne that finished at around midnight local time, having beaten Dino Prisnic – also in straight sets – in the first round.
He has won the Australian Open in the previous four years, and appears determined to once again retain his crown despite his ongoing injury issues.
He will face off against Tomas Martin Etcheverry – who beat Andy Murray – in the third round
The Serb also clashed with a fan in a heated exchange during his victory in Melbourne
‘I think I’ll be OK, to be honest,’ he said prior to the event. ‘But, you know, it did have quite an impact, particularly in the forehand and serve. But again, I don’t want to be spending too much time talking about it and taking away credit for the victory from De Minaur.
‘I mean, he was just very solid, as he always is, and congrats to him [and] to the Australian team. And, you know, it is what it is for us. I guess we move on and for me with my thoughts in Melbourne.’
He will face Tomas Martin Etcheverry, who knocked out Andy Murray on Monday – in the third round, having also clashed with a fan during the game.