SHANGHAI, China (AFP) — Daniil Medvedev got his revenge against American teenager Learner Tien, beating him in a nail-biter 7-6 (8/6), 6-7 (1/7), 6-4 on Wednesday to proceed to the Shanghai Masters quarterfinals.

There, he will meet world No. 7 Alex de Minaur, who cruised past Portugal’s Nuno Borges 7-5, 6-2 earlier in the day.

Victory in Shanghai comes just over a week after the 36th-ranked Tien took the Russian out of the China Open semifinals in Beijing.

“He’s an unbelievable tennis player,” Medvedev said of the 19-year-old.

“Outside of the big three, he may be the toughest opponent I’ve ever faced.”

Medvedev broke first in the ninth game, but Tien returned the favor immediately.

The last two games of the first set saw the two players locked in an epic back-and-forth, their prolonged rallies thrilling the crowd.

Both faced breakpoint but managed to hold, with Medvedev smashing a looping lob from Tien to send them to a gripping tiebreak.

Medvedev broke early in the second set, but Tien was again unphased — breaking back in the fifth and then seventh games, before the former world number one levelled in the tenth.

Medvedev began limping just before the second-set tiebreak and spoke briefly with a medic before hobbling back onto court.

Tien went 3-0 up as the Russian, 10 years his senior, tried to stretch out on court, becoming increasingly irate as the match was pushed to a decider.

“I should be calmer, but Learner drives me nuts. I lost two very traumatic matches against him — so for sure I was scared to lose again,” he said.