Spanish great Rafael Nadal says his suspect back remains a "day-to-day" proposition despite showing no signs of the injury while roaring into the Australian Open second round.
The 34-year-old skipped the ATP Cup due to the issue but looked in vintage touch against Serb Laslo Djere, banking a 6-3 6-4 6-1 victory on Rod Laver Arena on Tuesday.
"I'm happy to be through to the second round. I think I did a good job today," Nadal said.
"Straight sets, that's what I needed."
The world No.2 will move past absent Swiss Roger Federer to become the all-time grand slam leader with 21 titles if he takes the crown at Melbourne Park.
That feat looked very achievable, although Nadal said he had to alter his serve in his first official match in three months against the world No.56 due to his injury.
"Today it's not great and I needed to change a little bit the motion of my serve," the 34-year-old said.
"That's what I tried to survive that condition today and tomorrow a day off.
"I need to go day-to-day and just try to stay positive.
"Every day that I'm able to go through there are more chances to get better."
Nadal wasn't overly aggressive, with Djere hitting more winners, but the 2009 Open champion and five-times finalist who made the quarters last year, was able to nail the big points.
He saved two break points to snuff out the Serbian's challenge at 4-5 in the second set before wrapping up the third in just 28 minutes.