German third seed Alexander Zverev thanked his serve for guiding him past Learner Tien and into the Australian Open semi-finals.
According to BBC, the 20-year-old Tien, ranked 29th in the world, was bidding to become the youngest man to reach the last four in Melbourne for 34 years.
But Zverev produced a serving masterclass to reach his 10th Grand Slam semi-final with a 6-3 6-7 (5-7) 6-1 7-6 (7-3) victory on Rod Laver Arena.
A beaten finalist last year, Zverev fired down 24 aces and committed just one double fault alongside winning 76% of his first-serve points.
He saved all three break points he faced with an unreturned serve.
Zverev said, "Learner from the baseline was playing unbelievable. "I don't think I've played anyone who plays that well from the baseline for a very long time. Without my 20 aces - or something like that - I probably would not have won today, so I'm very happy with my serve."
Zverev said this year's Australian Open is the first time he has been playing "pain-free" in 12 months.
The 28-year-old tore ligaments in his ankle during his French Open semi-final against Rafael Nadal in 2022, a career-threatening injury that kept him out of action for six months.
Zverev has improved his serve in recent years, adding more consistency after double faults previously plagued his game.
In 2020, when he reached the semi-finals in Melbourne and the final at the US Open, he was averaging 5.9 double faults per match. He has improved on that figure every year since and, in 2025, his average stood at 1.9.
Zverev will face either world number one Carlos Alcaraz or sixth seed Alex de Minaur, the last Australian left standing in singles, in the semi-finals.
