(Photo credit: Geoff Burke)

Top-seeded Alexander Zverev secured the No. 1 spot in the ATP rankings for the first time with a 6-4, 7-5 victory over the Netherlands' Tallon Griekspoor on Thursday in the second round of the Erste Bank Open in Vienna.

The German did not face a break point and broke Griekspoor once in each set to reach his tour-high 13th quarterfinal of the season.

Zverev will become the 30th player to hold the No. 1 ranking when the new list is released Monday and the first German to reach the top spot since Boris Becker in 1991. The 29-year-old won the French Open and the U.S. Open this summer, and he reached the Wimbledon final.

His next opponent will be Great Britain's Arthur Fery, who defeated Lorenzo Musetti of Italy 6-4, 5-7, 6-4.

Second-seeded Carlos Alcaraz of Spain survived four set points in the second-set tiebreaker before beating Georgia's Nikoloz Basilashvili 6-1, 7-6 (11).

No. 3 Daniil Medvedev of Russia rallied past Great Britain's Cameron Norrie 4-6, 6-3, 7-6 (1), while seventh-seeded Tommy Paul routed Italy's Luciano Darderi 6-1, 6-1. Matteo Berrettini advanced when fourth-seeded fellow Italian Flavio Cobolli retired with an injury while trailing 5-2 in the opening set.

Swiss Indoors Basel

Swiss wild card Jerome Kym stunned top-seeded Ben Shelton 6-3, 6-7 (4), 7-6 (1) in the second round at Basel, Switzerland, while Germany's Jan-Lennard Struff eliminated fourth-seeded Novak Djokovic in another three-set upset.

Struff defeated Djokovic for the first time in nine career meetings, rallying for a 6-7 (4), 7-5, 7-6 (5) victory in 2 hours, 36 minutes. Djokovic failed to convert four break-point chances in the second set before Struff forced a decider, and the German closed out the final tiebreaker with an ace.

Monaco's Valentin Vacherot also knocked out a seeded player, edging No. 3 Rafael Jodar of Spain 7-6 (4), 2-6, 7-6 (5).

Second-seeded Arthur Fils of France avoided the upset bug by rallying past American Alex Michelsen 4-6, 6-3, 7-6 (5). Sixth-seeded Taylor Fritz of the United States dispatched Canada's Denis Shapovalov 6-4, 6-3, and No. 8 Jiri Lehecka of the Czech Republic defeated German lucky loser Daniel Altmaier 7-5, 6-4.

--Field Level Media