Alexander Zverev will be 29 years and 196 days old when the new ATP rankings are published, making him the second-oldest first-time world No 1 after Australian John Newcombe. (EPA Images pic)VIENNA: Alexander Zverev accelerated his ascent 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.