Rome - Simona Halep boosted her bid to retain her world No 1 ranking as the top seed advanced to the quarter-finals of the Italian Open after American Madison Keys withdrew injured on Thursday.
The Romanian, a finalist in Rome last year, is on her way to holding her top ranking as she next plays France's Caroline Garcia or American Sloane Stephens.
Halep needed to reach at least the last eight and go further than world No 2 Caroline Wozniacki to retain the top-ranking going into the French Open. Wozniacki plays her third round match later on Thursday.
Keys, the 2016 runner-up in Rome, withdrew from both singles and doubles, in which she was partnering Venus Williams.
"I felt my rib in my match yesterday and after trying to warm up this morning it was still painful," Keys said.
Venus Williams fell to her second defeat in a week to Estonia's Anett Kontaveit losing in the third round match in straight sets in 1hr 19min.
The 22-year-old Kontaveit won through 6-2, 7-6 (7/3) against her 37-year-old American rival who was seeded eighth in a tournament she won nearly two decades ago to 1999.
Kontaveit, who also beat Williams last week in Madrid, next plays either second seed Wozniacki or Latvia's Anastasija Sevastova for a place in the semi-finals.
Defending champion Elina Svitolina of the Ukraine fought back from a first set wipeout against Darya Kasatkina to win 0-6, 6-3, 6-2.
Fifth seed Jelena Ostapenko also needed three sets to get past Britain's Johanna Konta 2-6, 6-3, 6-4, with Germany's Angelique Kerber, seeded 11th, ending the hopes of Greece's Maria Sakkari 6-1, 6-1.
In the men's event, home hope Fabio Fognini reached the quarter-finals for the first time with a 6-4, 6-4 win over Peter Gojowiczyk.
Fognini was 4-2 down after a break in the first but won four games in a row against the German.
He next plays either top seed Rafael Nadal or Canadian Denis Shapovalov.
Results from the ATP and WTA Masters tournament in Rome on Thursday (x denotes seeded player):
Simona Halep (ROM x1) bt Madison Keys (USA x13) - walkover
Jelena Ostapenko (LAT x5) bt Johanna Konta (GBR) 2-6, 6-3, 6-4
Elina Svitolina (UKR x4) bt Daria Kasatkina (RUS x14) 0-6, 6-3, 6-2
Angelique Kerber (GER x11) bt Maria Sakkari (GRE) 6-1, 6-1
Anett Kontaveit (EST) bt Venus Williams (USA x8) 6-2, 7-6 (7/3)
Fabio Fognini (ITA) bt Peter Gojowczyk (GER) 6-4, 6-4
Pablo Carreno Busta (ESP x10) bt Aljaz Bedene (SLO) 6-4, 6-7 (3/7), 6-2
David Goffin (BEL x9) bt Juan Martin del Potro (ARG x5) 6-2, 4-5 - retired