ATP 500 ACAPÚLCO. By Leo Canaparo.
he American Learner Tien caused a major upset on Wednesday by eliminating the top favorite of the Mexican Open, German Alexander Zverev, to advance to the quarterfinals.
Tien secured a 6-3, 6-4 victory and will face eighth-seeded Tomas Machac. The Czech player had earlier defeated Daniel Altmaier, who came from the qualifying rounds, with a 7-6 (3), 6-1 win.
At 19 years old, Tien achieved the biggest victory of his career. His previous top achievement was defeating Daniil Medvedev, who was ranked fifth in the world at the time, in the second round of the Australian Open.
After reaching the fourth round of that tournament, Tien, a left-hander ranked No. 83, entered the top 100 in the world rankings for the first time in his career.
Zverev ended his Latin American tour on another low note. At the Argentina Open, he fell in the quarterfinals to local player Francisco Cerúndolo, while in Brazil, he was also eliminated in the last eight by another Argentine, Francisco Comesaña.