The seasoned 29-year-old proved a bridge too far for the 19-year-old American, who stunned fifth seed Daniil Medvedev in round two.
Against the world number 55, Tien wilted on a hot and humid day in Melbourne, succumbing 6-3, 6-2, 3-6, 6-2 with a right thigh problem not helping.
It brought the curtain down on a breakthrough debut tournament for Tien, who was bidding to become the youngest man to reach the quarter-finals since Goran Ivanisevic in 1989.
Instead, Sonego progressed to a last-eight clash with either French veteran Gael Monfils or American 21st seed Ben Shelton.
“Unbelievable. It’s pretty emotional, today was tough,” said Sonego.
“So sad because he had some problem. It’s not the right way to win but I’m so happy to reach the quarter-finals.
“Really special,” he added. “I’ve played really well this week and I want to enjoy every moment.”
Tien was broken to love on his first service game with the Italian giving him little opportunity to strike back, breaking again to secure the first set.
Sonego was untouchable on his first serve, winning 100 percent in set two, to again limit Tien’s chances.
The American slumped 5-2 behind before leaving the court for a medical timeout after treatment on his thigh.
When he returned, Sonego wrapped up the set with ease, but against the odds Tien recovered with a dominant break to start set three, holding on to give himself a glimmer of hope.
But he was spent as Sonego took charge again in the fourth set with the youngster flagging.
© 2025 AFP
