Canadian teenager Denis Shapovalov turned in a fighting performance in his first appearance at the Swiss Indoors on Monday, overhauling Japan's Yuichi Sugita 4-6 6-2 7-6 (7-3) in the first round.
Sugita won the opening set before the 18-year-old Shapovalov - who stunned Rafael Nadal in August in the Toronto third round - got into gear.
The youngster, who is seeking a spot in next month's ATP NextGen Finals in Milan, turned the tables as he lifted his level in a hard-hitting battle with a world No.38 opponent who claimed his first career title this season in Turkey.
Shapovalov, ranked 49th, won his 11th match of the season against nine defeats.
After Sugita claimed the opening set, Shapovalov started finding form, breaking twice to win the second set and square the match at a set each.
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In the third, the Canadian went up an early break but lost it as he dropped serve in the seventh game.
As the set went to a tiebreaker, Shapovalov dominated with a 4-2 lead, setting up three match points with a winning overhead.
The Canadian claimed victory on his first opportunity thanks to a Sugita double-fault.
"I had to fight to stay in it," Shapovalov said. "I won but I need to improve for the next round."
Spanish sixth seed Roberto Bautista Agut began with a win over Kazakh Mikhail Kukushkin 6-0 6-3. Korea's
Chung Hyeon beat Paolo Lorenzi of Italy 6-3 6-1.
Hometown hero Roger Federer heads the field as top seed, starting on Tuesday against American wildcard Frances Tiafoe.
Federer owns seven Basel title from a dozen finals.
