Nadal in their Australian Open quarter-final

audits for his victory over Nadal in their Australian Open quarter-final, a more worrying story was being largely overlooked.

Nadal's knees have failed him again and, for the second time in just over six months, he now surely faces a spell on the sidelines.

The big question has to be asked - is his career in doubt?

His conqueror Murray summed up the feelings of many fans with his post-match comment: "If it's the same thing, it's a big shame for him. I don't think he's the sort of player who deserves that.

"He obviously puts in everything into the game. He's great for tennis I always love watching him. I hope it's nothing too serious and I hope he's fine for the next tournament."

That may be wishful thinking.

Nadal confirmed it was indeed a "similar thing to what I had last year" when he spent two and a half months out with tendonitis, missing Wimbledon as a result.

How times have changed.

Twelve months ago Nadal sat at the summit of the game, some glorious tennis in Melbourne helping him become the owner of three of the four Grand Slam titles.

Having just captured a sixth Grand Slam title, there was talk among the tennis fraternity that Nadal could go on to rewrite the records of his peer Roger Federer, the ink on which was still wet.

I was among those salavating at such a prospect, but was also among the group wary of those knees - joints that have given Nadal problems since his early days on the tour.

Those fears were realised a few months later and now have emerged again.

You don't have to be a professor to know that rest is what's required to ease tendonitis - it's not a problem that you simply get rid of by undergoing surgery. And, of course, rest is not something a tennis player gets much of.

The knees take a pounding day after day, year after year and these days that pounding takes place on unforgiving surfaces such as the hard Plexicushion in Melbourne; probably not the best named surface in the world. Certainly the days when Rod Laver and co played largely on the grass - much easier on the body - are long gone.

While pundits like myself may well fear the worst for Nadal, the man himself was trying to stay positive in his press conference on Tuesday night - saying he felt he was going to be "OK" - and it's worth noting his comments there which shed some light on his long-standing knee problem.

The 23-year-old said he quit the match so not to "repeat the same mistake like last year". He added: "I go to the limit but not cross the limit (today)." So perhaps that will mean he won't need a two-and-a-half-month break this time.

Nadal also felt his game had been in good shape before he felt pain in his knee during the second set, telling the assembled press he was playing his best tennis since last year in Melbourne.

"I had big chances to win both sets. I was very close," he said.

"I go out from this tournament very happy about my level because the perspective is much better right now than two or three months ago when I lost in the Masters Cup (in London where he lost all three matches)."

Referring to his slide in form after winning Down Under in 2009, he added: "I played well few matches in Indian Wells. But after that started the pain. And after the pain, I didn't play bad, but far away from this level.

"For me it is a little bit disappointing to have the pain on the knee because I think I am very close to starting to win these important matches. And I think I'm going to do soon."

Fighting talk indeed.

One of the things most asked of Nadal is can he not change his defensive, run-all-day style of play in a bid to ease the pressure on his joints. For example, his matches regularly last considerably longer than Federer's who is able to hit more winners.

However, the Spaniard was annoyed by a similar question on Tuesday.

"Don't start with these questions right now. I think this is not the right moment. I think I changed the style. If you see my matches 2005 or 2004, 2006, I run a lot compared to now, no?"