Rafael Nadal said his back is still "not great" despite opening his Australian Open campaign with a routine straight-sets win.
The world No 2 pulled out of the ATP Cup last week with the niggle and said ahead of the Australian Open that he was "suffering".
He motored through his first-round clash against valiant Serb Laslo Djere with little drama, racing to a 6-3, 6-4, 6-1, victory under blue skies on Rod Laver Arena, but admitted he was still struggling.
"My back is not perfect, as I said a couple of days ago," said the Spaniard, whose only appearance this year had been an exhibition against Dominic Thiem in Adelaide 12 days ago, where he first experienced stiffness in his back.
"Every day that I'm able to go through, probably there are more chances to be better. That's the thing now.
"There is always a chance to improve, and that's why I'm here playing and fighting to try to get better and then give myself a chance."
The injury forced him to make changes in his service action against Djere, who didn't have the weapons to trouble the second seed despite Nadal being below par.
"Today it's not great. I needed to change a little bit the motion of my serve," he said.
"I need to go day-to-day and just try to stay positive. I'm trying to do all the things possible to be ready for compete - that's what I came here for."
It was his first competitive match since the semi-finals of the ATP Finals in London on November 21.
Nadal, bidding for a record 21st Grand Slam title, raced to a 3-0 first-set lead and wrapped it up before a tougher set two as Djere raised his first serve percentage and got himself in the rallies, with Nadal saving three break points.
But the unrelenting Spaniard was never in jeopardy, dominating off his first serve and outlasting the 56th-ranked Serb on the long rallies.
"I wish him all the best for the rest of the season," Nadal said. "Laslo has a great story. I wish him the best of luck."
Teenager Gauff eyes Svitolina scalp
A relaxed Coco Gauff said a carefree attitude had unlocked her precocious talent after the teenage sensation booked a second round Australian Open showdown with world No 5 Elina Svitolina.
The 16-year-old showed the form that fuelled her dazzling run last year at Melbourne Park during a crushing 6-3, 6-2 victory over Swiss Jil Teichmann in 56 minutes.
It was a commanding performance from the strong-serving American, who needed almost three hours to beat 58th-ranked Teichmann last week at the warm-up Gippsland Trophy.
"I put way less pressure on myself than I did last week and you can kind of see how the match played that I kind of played a little bit more free than last week," she said.
"I learned a lot from the summer series here, and I'm happy to take what I learned into this week."
The world No 48 was one of the best stories in Melbourne last year, where she upset reigning champion Naomi Osaka in straight sets in the third round.
Gauff quickly emerged as a fan favourite and became a vocal leader in the movement for racial justice in United States, where a speech she delivered in Florida went viral on social media.
Touted as the heir apparent to 23-time Grand Slam champion Serena Williams, her heady rise was tempered with early exits at the US Open and French Open last year.
Gauff said she had learned to cope with the high expectations.
"I don't feel any pressure," she said. "You want to do as well or even better than the year before, but I try not to think about it and just take it one match at a time."
She faces a difficult task to match last year's run, having to play consistent top-10 performer Svitolina on Thursday.
"She's a great player and I know it's going to be a tough match, but I'm just going to embrace the opportunity and try to play well under the pressure," Gauff said.
