World No2 Andy Murray may miss the French Open after a long-term back injury forced him to quit the Rome Masters.
"I'd be very surprised if I was playing in Paris," a subdued Murray said after retiring from a second-round start at the Foro Italico, handing a 6-3, 6-7 (5-7) win to Spain's Marcel Granollers.
The British ace, who celebrated his 26th birthday on Wednesday, said the pain in his lower left back that has bothered him since late 2011 flared up again recently, leading to his pullout from the Rome tournament.
"I felt pain today, the same as in Madrid. I hit yesterday and played some points. But I was still sore today," added Murray, with the French Open due to start on May 26.
There were no such problems for Madrid Masters champion Rafael Nadal, who began laying the groundwork for a dream seventh Rome title by hammering Italian Fabio Fognini 6-1, 6-3.