ROME, Italy - No.1 seed Simona Halep's defence of her top ranking was boosted on Thursday after No.13 seed Madison Keys withdrew from their third-round match at the Internazionali BNL d'Italia with a right rib injury.

The Romanian, a finalist here last year, needed to both reach the quarterfinals in Rome and progress further than World No.2 Caroline Wozniacki to retain her place at the summit, and has now accomplished the former task.

Keys, the 2016 runner-up in Rome, withdrew from both singles and doubles, in which she was partnering Venus Williams and due to face Raquel Atawo and Anna-Lena Groenefeld later today.

"I am really sorry I have to withdraw from this year’s Internazionali BNL d'Italia," the American said in a statement. "I felt my rib in my match yesterday and after trying to warm up this morning it will still painful. I look forward to returning to this great event next year and seeing all my fans in Rome."

As a result of Keys' withdrawal, the third-round singles match between No.11 seed Angelique Kerber and Maria Sakkari will be scheduled not before 1.30pm on Court 2, while the second-round doubles match between No.3 seeds Timea Babos and Kristina Mladenovic against wildcards Sara Errani and Martina Trevisan will be moved to Pietrangeli.

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