Melbourne, Jan. 25 -- American rising star Learner Tien produced a scintillating display at the Australian Open on Sunday, defeating three-time finalist Daniil Medvedev 6-4, 6-0, 6-3 to become the youngest men's singles quarterfinalist at the major since Nick Kyrgios in 2015.
The 20-year-old's triumph added another chapter to a rapidly developing rivalry. Twelve months ago, Tien, then ranked World No. 121, stunned Medvedev in a five-set second-round thriller in Melbourne, and later defeated the former World No. 1 again en route to his maiden tour-level final in Beijing.
This time, Tien dominated proceedings from the second set, winning 12 of the next 15 games after edging a competitive opening set. The victory was sealed in one hour and 3...