Home favourite Dominic Thiem makes winning start at Erste Bank Open in Vienna
Zverev squandered a 4-0 lead in the first set tie-break as Fritz claimed a 7-6 (8-6) 6-4 victory in an hour and 25 minutes.
“I played really solid, so it feels good to get that win instead of him getting me for the third time in a row,” said a delighted Fritz. “I got out there today and the sliders [on my serve] were working well.”
Third seed Stefanos Tsitsipas had to work hard to avoid a similar upset, the 21-year-old battling to a 6-3 7-6 (6) victory in the evening session against Spain’s Albert Ramos-Vinolas.
Moldova’s Radu Albot recovered from losing the opening set to beat Dusan Lajovic 2-6 6-3 6-4 and secure a second-round clash with top seed and nine-time champion Roger Federer.
Fifth-seeded Italian Fabio Fognini enjoyed a comfortable 6-2 6-4 win over Australia’s Alexei Popyrin, while American Reilly Opelka came out on top in two tie-breaks in a serving duel with Chilean Cristian Garin.
Opelka saved two set points in the second tie-break, finishing the contest with 27 aces and winning 98 per cent of points on his first serve.
Austrian Dominic Thiem started one of his favourite weeks of the season with a first win over Jo-Wilfried Tsonga, beating the Frenchman 6-4 7-6 (2) to reach the second round of the Erste Bank Open in Vienna.
Thiem will next face Fernando Verdasco, who beat Georgian Nikoloz Basilashvili 4-6 6-2 6-1, while South Korea’s Hyeon Chung overcame Milos Raonic 6-4 7-5.