Murray called for the trainer during his defeat in Rome
British number one Andy Murray lost 6-2 7-6 (7-5) to Stanislas Wawrinka in the second round of the Rome Masters.
With the French Open looming, the 20-year-old Scot struggled again on the clay and was broken twice in a first set in which he called for the trainer.
Murray, who later insisted he was not injured, rallied to take a 4-2 second-set lead, but Wawrinka broke back and sealed victory in a tie-break.
Wawrinka will now meet Juan Carlos Ferrero, who shocked Rafael Nadal.
Murray was desperate to find some form on clay ahead of the season's second Grand Slam but Wawrinka was stronger and more measured in Rome.
The Swiss world number 24 took an early advantage, breaking Murray for a 3-1 lead in the opening set.
I didn't feel that great first set, my legs were a bit heavy, but after that it was fine
Murray's situation was not helped as he appeared to hurt his left leg sliding for the ball and he called for the trainer.
The Scot complained about a tightness in his legs and after receiving treatment he conceded a second break with some wild groundstrokes.
Just as he slumped in the opener, Murray seized the momentum in the second, immediately breaking Wawrinka and taking a 2-0 lead.
His renewed resolve and focus saw him fend off break points in the fourth game but when Wawrinka pushed him at 4-3, the Briton lofted his drop-shot wide to surrender the break.
The Swiss almost sealed victory on Murray's next service game but the Scot fought back from 0-40 with some brilliant play to level at 5-5.
A tense set between the two off-court friends was settled by a tie-break and Murray's inability to deliver a strong first serve was telling.
The Scot failed to hit an ace throughout the entire match and when he needed a big serve most he could not find one, and was forced to try to out-play Wawrinka with his groundstrokes.
Murray saved another match point at 6-5 but went long at the crucial moment to hand the Swiss the match and a third-round tie with Ferrero, who upset second seed Nadal.
Afterwards, Murray insisted that injury had played no part in his defeat.
"I didn't feel that great first set, my legs were a bit heavy, but after that it was fine," he said. "I didn't feel that great, that's all.
"I saw the physio and the doctor and just got some hot cream. The doctor gave me a vitamin tablet or something - I don't know exactly what it was - and, yeah, I felt fine."
BBC Radio 5 Live tennis correspondent, Jonathan Overend, said: "Murray started feeling his groin in the third game of the match and really struggled for movement in the whole of the first set.
"It did improve after treatment from the trainer but his assessment afterwards of just heavy legs and poor tennis came as a big surprise to those who watched the match and were expecting a full medical bulletin."