Despite multiple attempts, Zverev hardly closed the gap on No. 1 Jannik Sinner, who has barred from tennis competition since February.

World No 2 Alexander Zverev was knocked out of the Madrid Open in the round of 16 by Argentina's Francisco Cerundolo on Tuesday as defending women's champion Iga Swiatek had a few scares before advancing to the quarter-finals. Cerundolo, ranked 21, beat the German -- a two-time former winner in Madrid -- 7-5, 6-3 to repeat his feat from last year.

Iga Swiatek advanced to the quarterfinals of the Madrid Open after a "more relaxed" day following a blackout while top-seeded Alexander Zverev was upset by Francisco Cerundolo.