World number one Naomi Osaka has pulled out of the Italian Open before Thursday’s quarter-finals with injury.

The 21-year-old withdrew because of a “pain in her right hand,” organisers announced.

The Japanese star was due to meet Madrid Open champion and sixth seed Kiki Bertens for a place in the final four in Rome.

Osaka, the top seed, won twice on Thursday to enter the quarter-finals. With the two wins, she retained the world number one ranking ahead of the start of the French Open.

In her last 16 match, Osaka eased past Mihaela Buzarnescu 6-3 6-3 after earlier beating Slovak Dominika Cibulkova by the same scoreline.

Osaka was at risk of losing her world number one ranking to Simona Halep but the Romanian was knocked out by Czech teenager Marketa Vondrousova losing 2-6, 7-5, 6-3.