(Photo credit: Robert Deutsch-Imagn Images)

German veteran Jan-Lennard Struff outlasted top-seeded Karen Khachanov of Russia, 4-6, 7-6 (5), 6-3 on Thursday in the second round of the Almaty Open in Almaty, Kazakhstan.

Struff, the 98th-ranked player in the world, was broken in the first game and made little headway on Khachanov's service games in the first two sets. But the 35-year-old raced out to a 4-1 lead in the second set tiebreaker and held on, 7-5, to send the match to a deciding set. Struff kept the momentum, breaking Khachanov in the third set's opening game and closing the upset on his fourth match point.

Struff racked up 43 winners to only 16 unforced errors in the contest, though Khachanov won one more point, 108-107, during the 2-hour, 21-minute match.

In other second-round action, second-seeded Daniil Medvedev of Russia edged Australia's Adam Walton, 7-5, 7-6 (0), Japan's Shintaro Mochizuki stunned No. 4 Luciano Darderi of Italy, 6-3, 6-3, and Alex Michelsen needed only one hour to defeat Australian Aleksandar Vukic, 6-3, 6-2.

Nordic Open

Top-seeded Holger Rune of Denmark knocked off Hungary's Marton Fucsovics, 6-4, 6-4, in the second round of the Nordic Open in Stockholm, Sweden.

Rune got up a double-break and held off Fucsovics in the first set, then broke to open the second set and wrapped up the win on his third match point. Fuscovics earned nine break-point chances, but only converted one. He struggled at the net, winning only 11 of 20 attempts.

Fourth-seeded Ugo Humbert of France eliminated Italy's Matteo Berrettini, 7-6 (5), 6-3, while Italy's Lorenzo Sonego, Argentina's Tomas Martin Etcheverry and the host nation's Elias Ymer also triumphed. Ymer, ranked No. 243, cruised past Great Britain's Jacob Fearnley, 6-2, 6-2 and will face No. 3 seed Denis Shapovalov of Canada in the quarterfinals on Friday.

Fortis European Open

Canadian Felix Auger-Aliassime, one of the hottest players on the ATP Tour, needed nearly three hours (2 hours, 57 minutes) to uphold his No. 2 seed and defeat Bosnia and Herzgovina's Damir Dzumhur, 7-6 (3), 4-6, 7-6 (5) during second-round action in Brussels, Belgium.

Dzumhur staved off three match points at 5-4. With the deciding tiebreaker knotted 5-5, the Canadian earned the 11th point on his opponent's serve and held on to advance to the quarterfinals. He will face Eliot Spizzirri, who raced past the Netherlands' Botic Van De Zandschulp, 7-5, 6-0.

Top-seeded Lorenzo Musetti of Italy prevailed in a tight match versus Germany's Yannick Hanfmann, 7-6 (3), 7-5. France's Giovanni Mpetshi Perricard needed to win just one set to advance as Georgia's Nikoloz Basilashvili retired after dropping the first set 7-5.

--Field Level Media