Novak Djokovic battled with a lower back injury as he claimed his 11th round of 16 appearance at the Australian Open on Saturday.
The six-time champion advanced with a clear-cut 6-2, 6-3, 6-3 win over Spanish 21st seed Albert Ramos-Vinolas in 2hr 21min on Margaret Court Arena.
But there was concern in the Serb`s camp when the former world No.1 sought a medical timeout early in the second set for treatment to his lower back.
Djokovic, looking for matches after six months out with right elbow trouble, will next face South Korea`s Chung Hyeon in Sunday`s fourth round after he shocked Alexander Zverev.
The injury was a fresh concern for the 12-time Grand Slam champion, whose ranking has slipped to 14 after an inactive second half of 2017.
But Djokovic was workmanlike as broke the Spaniard`s serve five times, although his errors outnumbered his winners 40-37.
"It was a straight sets win, but it was almost two-and-a-half hours, so it wasn`t that easy and comfortable on the court," Djokovic said.
"I knew coming into the match that he was a great fighter, he grinds it out and gets a lot of balls back.
"Obviously for me it`s taking it one match at a time but I have to be more humble with my expectations as I haven`t played in the last six months.
"But I am very pleased where my game is at."
Should Djokovic beat Chung he is facing a potential quarter-final against Austria`s fifth seed Dominic Thiem, who must first get past American surprise packet Tennys Sandgren on Monday.