John Millman has shown former world number three Dominic Thiem how hard it will be to climb his way back to the elite level, ending the Austrian's return to action at the first hurdle in Belgrade.
Millman — world number 80 — won 6-3, 3-6, 6-4 in a 2-hour, 35-minute tie to reach the Serbia Open's second round.
Thiem was playing his first tour-level match since injuring his right wrist last June, subsequently undergoing surgery.
At the time, Thiem had been in the world's top five for more than three years. However, inactivity since then sees him outside the top 50.
"I can't claim it was one of my biggest wins because he is just coming back from injury and I know how hard that is, coming back from three surgeries myself," said Millman of Thiem.
"I know it has been tough for Domi but the game is better having him back. Especially on this surface.
Millman has won 10 of his 17 tour titles on clay and said: "It is great to be back here. I was looking forward to coming back and playing [here].
Millman, 28, broke in the 10th game of the third set, going on to book a last-16 meeting with seventh-seed Miomir Kecmanović, who beat Richard Gasquet 6-0, 6-3.
"I expect a few more [fans] to be going for Kekkers tomorrow," Millman said of his Serbian opponent.
"I played him in practice a few days ago and he chopped me.
"He is seeing the ball massive and has had a great, six-week run. It is going to be a tough match but it's exciting to play these young guys and test yourself against them."
The winner of that match is scheduled to face host Novak Djokovic at the venue that bares his name — the Novak Tennis Centre — in the quarter-final.
At the Barcelona Open, Jordan Thompson lost 6-4, 6-2 to Hungarian world number 53, Márton Fuscovics.
The other Australian in the 48-man field, Alex de Minaur, had a first round bye.
In the second round he will face Ugo Humbert, who defeated Pablo Andújar 6-4, 6-3.
Tsitsipas, the top-seed, will face 44th-ranked Belarusian Ilya Ivashka on Wednesday.
AAP/ABC
