Stefanos Tsitsipas saw his hopes at the Adelaide International dashed at the first hurdle as he suffered a shock defeat in straight sets to home hope Aleksandar Vukic.

Qualifier Vukic emerged triumphant after two close sets both went to a tie break, winning 7-6 (7-3) 7-6 (7-5) in one hour and 53 minutes on Tuesday.

Neither player managed a break of serve in what was an even contest, though Vukic was comfortably able to win the first breaker.

He had to work much harder in the second tie-break, rallying from 3-1 down to claim six of the next eight points and successfully convert his first match point.

Seventh seed Tsitsipas had gone 3-0 at the United Cup last week and was hoping to build further momentum ahead of the Australian Open with a strong run this week, as he looks to bounce back from an injury-hit 2025 season.

But instead it is Vukic who will take on Andrea Vavassori in the last 16, after prevailing in front of a loud Australian crowd.

"I am just in awe of this stadium and the cricket ground that is just here," Vukic said to the fans at Memorial Drive Tennis Centre after his victory.

"This centre court is very special, and it is pretty packed. I appreciate the support, everyone helping me out. It was an awesome win for me."

Victory for Vukic 

Aleksandar Vukic defeats Tsitsipas 7-6, 7-6 to advance in Adelaide!@AdelaideTennis | #AdelaideTennis pic.twitter.com/nnnFlPQxjd

— ATP Tour (@atptour) January 13, 2026

Top seed Alejandro Davidovich Fokina will open his campaign at the ATP 250 event on Wednesday against Rinky Hijikata, who defeated Tristan Schoolkate in straight sets.

Data Debrief: Serve dominates close encounter

Tsitsipas was beaten despite serving incredibly well. He won 88% of his points on first serve (44/50) and fired down 13 aces in the match.

But he could not find a way to break Vukic, failing to even reach a break-point opportunity in the opening set.

The Greek star did force four break opportunities in the second set, though was unable to convert.

Tsitsipas actually won more points (87 to 84) in the match, but exits the tournament after Vukic delivered at the key moments.