World No. 1 Novak Djokovic says that his abdominal pain was bearable in his fourth-round victory over Milos Raonic on Sunday, but competing at the Australian Open “was kind of a gamble”.

The eight-time champion, who suffered the injury in his five-set victory over Taylor Fritz on Friday, underwent an MRI scan in Melbourne and did not practise ahead of his clash against Raonic on Rod Laver Arena.

“It's kind of a gamble,” said Djokovic, who had his abdominal muscles taped up against Raonic. “That's what [the] medical team told me. It's really unpredictable… It could cause much more damage than it is at the moment, but it also could go in a good direction. So that's something that I don't know, and I don't think I will also know until I stop taking painkillers.

“As long as I'm with high dose of painkillers, I guess, still [I] can bear some of the pain. But the tricky thing with the painkillers is that they kind of hide what's really happening in there, so you might not feel it, but then the big damage might be done.”

Djokovic, who will next play sixth seed Alexander Zverev at the Australian Open so soon after their epic ATP Cup clash, admitted he took the decision to play Raonic only a few hours before the match began.

“I didn't know [a] few hours before I stepped on the court tonight whether I was going [to] play or not,” said the 33-year-old. “I didn't hit a tennis ball yesterday. I tried to use every single hour possible to recover and give myself at least a little bit of chance to step on the court, which I have done.

"But I somehow managed to find a way and win, and that's what matters the most. Now I've got another 40 hours or something like that until the next match, which is great about Grand Slams. You get that day, [a] day-and-a-half in between to really rest. So, most likely, I won't be training tomorrow and just go back to [my] recovery routine and hope that things will get better.”

Asked about the potential long-term effects of the injury, Djokovic added, “I have talked a lot with my own medical team and also the medical team of Tennis Australia — the Australian Open. They all share the opinion that there is a slight, very slight, slim chance that I will make significant damage that would take me out of the Tour for [an] extended period of time.

“There is always a risk that the injury will get worse, but they don't think it's going to be very significantly worse that it's going to jeopardise my entire season… I really don't know exactly how far I'm going to go with this injury or how far I'm going to go in the tournament. There is still potentially three matches to go, and it's only going to get tougher and tougher for me on the court.”

Djokovic has a 5-2 lead in his FedEx ATP Head2Head series against Zverev, who beat No. 23 seed Dusan Lajovic in straight sets on Sunday.