Madrid, May 6 (IANS): Defending champion Alexander Zverev reached the fifth consecutive quarter-final at the Madrid Open after Lorenzo Musetti was forced to retire from the pair's third-round clash at the ATP Masters 1000 event, here on Thursday.

Zverev led 6-3, 1-0 in what had been a high-quality first head to head meeting between the two when a thigh injury to 20-year-old Musetti intervened in Arantxa Sanchez Stadium.

The World No 3 led the Italian after converting the only two break points of the first set in the seventh and ninth games. Zverev now holds a 17-2 record in Madrid, where the fast conditions suit his big-serving and high-powered game.

Although the German had to dig deep in his three-set win over former World No 3 Marin Cilic in the second round, second-seeded Zverev looked in impressive touch against Musetti and will eye another deep run in the Spanish capital as he hunts a sixth Masters 1000 crown.

Zverev's opponent in his 23rd Masters 1000 quarter-final will be eighth seed Felix Auger-Aliassime or 10th seed Jannik Sinner.