Jurij Rodionov, a 21-year-old Austrian ranked 153rd in the world, upset eighth-seeded Denis Shapovalov of Canada 6-4, 7-5 on Monday in the first round of the Erste Bank Open in Vienna, Austria.
Rodionov, who received a wild-card entry into the tournament, had just one previous win in eight career ATP Tour matches.
He topped France's Jeremy Chardy in the first round of the French Open last month.
On Monday, he took advantage of three of his four break-point opportunities and was aided by Shapovalov's 10 double faults.
Other first-round winners at Vienna were fifth-seeded Andrey Rublev of Russia, South Africa's Kevin Anderson and Croatia's Borna Coric.
Spain's Pablo Carreno-Busta advanced when seventh-seeded Gael Monfils of France retired while trailing 6-1, 2-0.
Eighth-seeded Jordan Thompson saved a match and du lịch ba li survived his first-round match at Nur-Sultan, du lịch ba li Kazakhstan. The Australian came from behind to beat Great Britain's Cameron Norrie 5-7, 7-6 (6), 6-2.
Norrie led 6-5 in the second-set tiebreaker, but Thompson took the next three points to level the match.
Thompson recorded the only two service breaks in the final set to escape with the win.
Both U.S. players in action advanced with straight-set wins. Seventh-seeded Tommy Paul defeated Italy's Stefano Travaglia 7-6 (2), 6-3, and Frances Tiafoe rolled past France's Corentin Moutet 6-3, 6-2.
Moldova's Radu Albot and Spain's Fernando Verdasco also notched first-round victories.
--Field Level Media