By Chris Bailey BBC Interactive in Paris

Murray's physical problems caught up with him again in Paris

Roger Federer said last week that Andy Murray is not in the best shape he could be and when the world number one speaks, you sit up and listen.

Lleyton Hewitt's view is that the longer he keeps Murray on court, the better chance he has of coming out on top, and I'm sure he's not the only player who thinks like that about the 19-year-old.

We've had cramping at Queen's and Wimbledon, vomiting at the US Open, cramping again at Monte Carlo and now a lower back problem in his defeat to Gael Monfils at the French Open.

It is all very unfortunate but let's not start thinking this is a mental problem for Andy.

One of Andy's major strengths is his mental fortitude and I think he proved that against Monfils in the opening three sets.

However, it is clear that he has a lot of hard work to do and a lot of pain to go through to get to a level where he is strong enough to go the distance: not just for one match but for seven.

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Until he puts in that hard graft, his body will always let him down.

But the problem Murray faces is very similar to the one faced by Maria Sharapova on the women's tour: to increase your fitness, you need to increase your workload, but if you increase your workload while you're still growing, you risk a long-term injury.

Murray has to be worried about what his body is telling him and that is why he, as well as his former coach Mark Petchey, is convinced we will not see the best of him for at least two years.

We have to remember that he is only 19 and he has not even had a full year on the tour yet.

He knows as well as anyone he has to improve his fitness, but if you look at the way he constructs points and the way he strikes the ball, there is still an enormous amount to be excited about.

But with Wimbledon approaching, it is also a time for realism.

Andy will not win Wimbledon.

Hopefully he can go further than the third round, which is what he did last year, but if does get to the last 16, it will have been a very, very good tournament for him.