Is Nadal human?

I for one am now willing to admit I am wrong...

Although Rafa is No.1 in the world right now, I certainly failed to consider him as a serious contender to win the Australian open this year. And yes, while everyone was getting caught up in the big debate over whether Andy Murray should be the favourite, Nadal was quietly destroying people without getting caught up in such arguments involving mere mortals.

But questions need to be asked...

His knees have often been likened to breaksticks, likely to crumble with the softest touch, but yet he still going. Although he has worked to reduce the ridiculous amounts of spin he puts on his shots he still enjoys a good baseline rally, chasing down the impossible drop shot or darting across the court to send a running passing shot straight back at his demoralised opponent.

So if we are to consider Nadal human rather then some sort of tennis machine sent from the future to reduce Roger Federer to a whimpering mess, just exactly when is his motor going to start stalling?