(CNN) -- Andy Murray's birthday celebrations were brought to an abrupt halt after his plans to compete at the French Open were thrown into jeopardy on Wednesday.
A long-term back injury looks set to sideline the world No. 2, who was forced to retire from his second-round match at the Rome Masters on the day he turned 26.
And with the Paris showpiece event set to begin on May 26, Murray faces a race against time to prove his fitness.
"I'd be very surprised if I was playing in Paris," the British star, who lost in the quarterfinals in Madrid last week, told reporters following his match against Spain's Marcel Granollers.
"I felt pain today, the same as in Madrid. I took a few days off after Madrid. I hit yesterday and played some points. But I was still sore today."
The pain in the lower left of his back has caused Murray discomfort since late 2011 and is the same injury which required a painkilling injection at last year's French Open.
"We will have to wait and see on Paris," he said. "I'll try to make a decision after the next five days or so. I need some days off for it to hopefully settle down."
Murray's retirement came as something of a surprise after he had fought back from losing the opening set 6-3 and being down 4-1 in the second to level the match following a tiebreak.
But after undergoing on-court treatment with the trainer early in the second set, Murray decided to call time on his Rome challenge.
It is the first time since 2007 that Murray has retired during a contest -- that was at the Hamburg Open where he suffered a wrist injury which ruled him out of the French Open and Wimbledon.
Murray, who has never won a clay-court title despite training on the surface as a young teen in Spain, reached the quarterfinals at Roland Garros last year.
But the U.S. Open and Olympic champion now looks unlikely to challenge for the title in the French capital.
"(The back) has not been perfect for a long period, I want it to start feeling good again," the Scot said.
"Everyone goes into matches with niggles, but this is very frustrating.
"Some shots hurt more on clay because the movement is so exaggerated. There is not a lot of power on the ball so you have to generate power and pace yourself.
"I don't want to go into details, but I've got a disc problem, it changes week to week. It's been an issue for a while, but I want to make sure it goes away.
"I don't want to be playing with it long term, it's not enjoyable at all."
Elsewhere, French eighth seed Jo-Wilfried Tsonga suffered a shock defeat by Jerzy Janowicz, going down 6-4 7-6. The 24th-ranked Pole ripped his shirt off in delight after his best result this year, earning a clash with French ninth seed Richard Gasquet.
In the women's section, defending champion Maria Sharapova eased to a 6-2 6-2 win over Spain's Garbine Muguruza.
Former French Open winner Li Na overcame Chinese compatriot Zheng Jie 6-3 6-1 as she bounced back from her first-round defeat in Madrid, while there were also victories for Samantha Stosur, Maria Kirilenko and home favorite Roberta Vinci.