Croatian Borna Coric recovered from a set down to beat three-time Grand Slam winner Stan Wawrinka 4-6, 6-4, 6-3 in the opening round of the Shanghai Masters on Monday.
Coric, who had failed to win a match in his last two appearances in Beijing and Shenzhen, saved two break points at 3-3 in the second set and clinched the first four games of the decider to record his 32nd match win of the season.
It was Coric's first victory in four meetings against former world number three Wawrinka, who has struggled on his return from knee surgery this season and entered as a wildcard.
Coric, seeded 13th, will next face American qualifier Bradley Klahn, who claimed a hard-fought 4-6, 6-4, 6-3 win over Nick Kyrgios.
The 23-year-old Australian Kyrgios lost five straight games from 4-4 in the second set to hand the momentum to Klahn.
World number 104 Klahn. who fired down 18 aces, recorded just his fourth tour-level win of the season.
Greek youngster Stefanos Tsitsipas, whose run to the quarter-finals in Tokyo last week was enough to book a place at the ATP Finals in November, opened his Shanghai campaign with a 7-6(4), 4-6, 6-4 win over Gael Monfils.
The 20-year-old broke the Frenchman's serve twice in the decider to set up a second round meeting with Russian Karen Khachanov.
"I have improved a lot since last year physically, mentally," said 10th seed Tsitsipas.
"My game has changed. I am more aggressive now. I'm actually stronger. I feel stronger. My body has changed since last year.
"I have (now played) lots of matches in the ATP main draws, lots of wins which gave me confidence. I believe in myself a little bit more."
Canadian Milos Raonic suffered an early exit as the 2016 Wimbledon finalist lost to American qualifier Mackenzie McDonald 6-3, 5-7, 6-3.
Big-serving American Sam Querrey struck 14 aces on his way to a 6-3, 6-4 win over world number 16 Diego Schwartzman and set up a second round meeting against his compatriot Taylor Fritz, who beat Robin Haase 6-3, 7-6(3).
Pliskova sees off Lepchenko in Tianjin opener
Former World No 1 Karolina Pliskova overcame unseeded Varvara Lepchenko 6-2, 6-7(3), 6-3 in her opening-round match at the Tianjin Open on Monday.
The 26-year-old Pliskova, who took a wildcard entry into the tournament as she aims to qualify for the season-ending WTA Finals in Singapore, eased through the first set but Lepchenko's aggressive forehand caused her problems in the second and the American won the tiebreaker to force a decider.
Lepchenko saved five match points on the back of some powerful groundstrokes but a solid first serve clinched Czech Pliskova's win after two-and-a-half hours.
Top seed Pliskova will next face Slovenian Polona Hercog, who beat Spain's Lara Arruabarrena 7-6(5), 6-2.
Pliskova is chasing one of the three available spots in the WTA Finals, along with fourth seed Aryna Sabalenka, Sloane Stephens, Elina Svitolina and Kiki Bertens.