Alexander Zverev accelerated his ascension to number one in the world rankings for the first time in his career on Thursday as he beat Tallon Griekspoor 6-4, 7-5 to reach the quarter-finals of the Vienna Open.

The 29-year-old German was already assured of finishing the season top of the ATP rankings but, in the absence of current incumbent Jannik Sinner, two-time Grand Slam champion Zverev will now take that crown in next week's updated standings after winning his opening two matches in the Austrian capital.

Long seen as tennis' nearly-man, Zverev has enjoyed a stellar 2026, breaking his major duck by picking up the titles at the French and US Opens.

Now he has broken further ground by becoming only the 30th man to claim top spot since the rankings were first published in 1973.

He will be aged 29 years and 196 days when Monday's new rankings are published, making him the second-oldest first-time number one after Australian John Newcombe.

Due to a knee injury Italy's Sinner decided to end his season at the start of October, opening the way for Zverev to dethrone him.

And the big-serving Hamburg native ensured he did just that ahead of the season-ending ATP Finals next month by seeing off Martin Landaluce and Griekspoor in his opening two matches in Vienna.

Zverev needed to save four match points against Spain's Landaluce in his first-round match on Tuesday, but was much more comfortable as he defeated Griekspoor in straight sets to write his name into the history books.

He raced out of the blocks on Thursday, breaking the 30-year-old Dutchman in the very first game and then confidently serving his way into a one-set lead.

The second frame went to 5-5 before Zverev pounced on Griekspoor's serve to get his nose in front.

The match met an unexpected stoppage as Zverev brought up match point when a smash off the German's racquet caused part of the electronic board behind Griekspoor to malfunction.

But once the umpire covered the problematic panel up with a towel, Zverev then sealed his new ranking with an unreturnable serve.

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