Swiss says timing rather than nature of injury that prompted French Open withdrawal will be of greatest concern.
Juan Martin Del Potro has been forced to withdraw from the French Open due to an ongoing viral infection.
World number one Novak Djokovic accepts Rafael Nadal starts as favourite at the French Open.
Highest remaining seeds Gilles Simon and Sam Querrey both eased into the quarter-finals of the Open de Nice Cote d'Azur.
Australian Bernard Tomic will play at next week's French Open despite his off-court troubles.
Argentine former US Open champion Juan Martin del Potro has withdrawn from the French Open because of a virus.
Top seed Caroline Wozniaki was sent crashing out of the Brussels Open after suffering a 6-2 6-4 second-round defeat to Zheng Jie.
Fourth seed Hsieh Su-wei was dumped out of the Internationaux de Strasbourg after being beaten a 6-4 4-6 7-6 (7-3) by Misaki Doi in the second round.
Exclusive interview: Heather Watson reveals to Simon Briggs she's fit for French Open after two months battling glandular fever.
British No 2 Heather Watson is ready to return to action at next week's French Open in Paris after overcoming glandular fever.

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