Novak Djokovic held off Frenchman Quentin Halys 7-6 (7/3), 7-6 (7/5) on Thursday to reach the Adelaide International quarter-finals.
The Serbian did not get the perfect start he wanted as he lost his opening service game against the 64th-ranked Halys and had to battle back from 5-2 down in the first set.
The game however went to a tiebreak in the second set as nothing could separate the duo.
In the end, Djokovic, who was unable to defend his title last year because he was deported on the eve of the tournament, produced a vintage performance to claim the match with a pair of tiebreak wins.
"It was a great performance from my opponent today. I want to congratulate him for great quality and a great fight.
"Tough luck but he played like a top-10 player today, no doubt," the 35-year-old Serb said of Halys.
"As far as my game goes, I feel good on the court. I didn't have such a great start, I lost my serve early.
"He was serving really well, fast, big serves, hitting his spots in the box very well.
"Just difficult to play in this kind of court that is really fast. It kind of favours the server.
"If you're serving well, it's tough to break the serve of a big server like him, so two tiebreaks were probably the most realistic score."
The outcome of the game means that Djokovic, now ranked fifth in the world, will next play world number 18 Denis Shapovalov, who he has beaten in all seven of their meetings.
Shapovalov booked a spot in the last eight with a 6-4, 6-3 win over Russian qualifier Roman Safiullin.
"Denis is one of the most complete players out there, he's got a very dynamic style of tennis, a big serve, comes to the net and comfortable playing from the back of the court.
"He's a very great athlete, moves fantastically. We haven't played for a while so I'm looking forward to that.
"Every match now gets tougher, I'm going to be ready for that," Djokovic added.