Andy Murray, the teenage star of British tennis, discovered that growing up can be a real pain after suffering another worrying tournament exit because of his fragile physique.

The 19-year-old Scot suffered a lower-back injury in the second set tie-break against French teenager Gael Monfils which effectively robbed him of a place in the second round of the French Open.

Murray battled on to take a two-sets to one lead, but eventually succumbed to Monfils in five sets 6-4 6-7 1-6 6-2 6-1, in three hours and 42 minutes.

It was a valiant display from the youngster from Dunblane on a chilly afternoon which was anything but what the doctor ordered for a bad back.

But despite damaging an ankle at Queen's last year, cramping on court at Wimbledon, vomiting on court at the US Open and appearing to struggle for fitness in his longest matches, Murray's message was 'don't panic'.

An X-ray in Germany at the end of last year diagnosed that Murray's spine was not fully grown. The remedy is time and maturity and Murray showed plenty of the latter even in the disappointment of defeat.

Murray said: "There's no need to panic. I'm only 19. I'm hopefully going to play these tournaments for the next 12, 13 years.

"It's disappointing that I couldn't finish the match how I would have liked. But I'm pretty well grounded. I realise where I'm going and how many chances I'm going to get to play in these tournaments.

"When you have a slight weakness in your lower back because you're still growing you can't push too hard or you're going to hurt yourself.

"I hope I'm going to stop growing this year so at the end of the year I can really get myself in my best shape."

Doctors have told Murray the growing problem is probably the reason for his frequent cramps, a condition which last affected him badly in first-round defeat against Jean-Rene Lisnard in Monte Carlo in April.

The cure is growth but the immediate remedy is an exercise programme to strengthen the lower back.

If the injury had not struck, Murray was convinced he would have won against a player he beat convincingly in Hamburg last week.

He was probably correct, although it was an intriguing encounter between two players who will entertain tennis fans over the next decade with their ability to blend power and delicacy.

The first set was halted for five minutes for a rain shower after Murray had won the first game but while he returned to race into a 3-0 lead, it was Monfils who proved the pedigree which has sped him to a world ranking of 28, reeling off five successive games.

Murray began the second set strongly, this time racing into a 4-2 lead in a match was rapidly becoming a duel of deft drop shot and counter drop.

In the eventual tie-breaker Murray took the initiative, a brilliant backhand down the line seeing him take the breaker 7-2. Little were we to know then that his back had seized on a first serve at 5-2 in the breaker.

We found out when he called for the trainer at the changeover as he led 3-0 in the third. He received treatment, lying flat on court, but even though he ran through the set against an opponent who appeared to be even more affected by the interval, he was in obvious pain.

He was rolling in his first serves at around 50-60mph and suddenly the Frenchman was in total control, taking five successive games in the fourth set as Murray spasmodically grimaced.

Not that it stopped the Frenchman questioning what seemed like every other line call.

Murray added: "I was disappointed with him. You know you are acting up a bit when your own crowd is booing you. He did the same to me in Hamburg when he was trying to say it was a different mark. I don't think he needed to do that."

The fifth set was a mere formality, Monfils running out an easy winner as Murray continued to struggle.

If the physical problems continue - and constant lunging and high bounces on clay do not help - they are bound to play on Murray's mind.

For now, however, he is looking forward to the grass-court season.

He said: "I've got 11, 12 days before Queen's. The grass is pretty soft, doesn't put too much strain on your body. I've got enough time to see the physio and get a lot of massage and do some exercises to get it better. I should be okay."

It leaves Tim Henman, someone else who knows all about back problems, as the last Briton standing in Paris. He plays Russia's Dmitry Tursunov in the second round tomorrow.