German third seed Alexander Zverev thanked his serve for guiding him past an “unbelievable” Learner Tien and into the Australian Open semi-finals.
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.
“Learner from the baseline was playing unbelievable,” Zverev, 28, said.
“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.”