As we enter another tournament without Rafael Nadal, is it time to start worrying about just how bad the Spaniard's knees are? And is he capable of recovering quickly and getting back to his top level?
I do not want to write him off just yet, as I remember thinking when he pulled out of Wimbledon in 2009 it might have been the beginning of the end but he roared back to his best.
You have to be worried about the noises he is making though. He is such a good guy and has been such a major force in the game that everybody is really rooting for him to get back to his best.
You are naturally going to be more worried when Rafa gets injured than with anyone else simply because of the way he plays. Nobody puts as much wear and tear on their bodies in the world of tennis — and nobody ever has done, either.
There will come a time when his body finally says 'no more' - and I really did think that time had come three years ago.
I was surprised but very impressed at how he managed to squeeze out even more success after that setback and went on to achieve even greater things and maybe he can carry on for another three years or more and achieve even more.
However, because it is Rafa and because we all care so much about him, you do wonder what might be in store - when he gets injured it certainly is more concerning than when it happens to Novak Djokovic or Andy Murray, whose bodies don't look as likely to break down.
Looking ahead to the hard court season, it is hard to identify which player is coming into it in the best shape.
Andy Murray will certainly be full of confidence after his victory at the Olympics. That was on the grass at Wimbledon but it was still relevant.
In some ways he has got a monkey off his back. The British public were beginning to believe that he was a loser. Of course, those of us in tennis know this has never been the case, but being able to call himself Olympic champion will get some people off his back.
Would he have swapped the Olympics for Wimbledon? Of course he would. A Grand Slam remains another rung up the ladder. The Olympics is not the 'be all and end all' of tennis like it is in other sports, you can't deny that.
However, you also can't write off its significance. It was a huge achievement beating Djokovic and Roger Federer back-to-back to win the gold.
It will help psychologically going into the US Open and he should be in a very positive frame of mind. There is no doubt Federer was off his game in the final - I'm not sure if there was something underlying there like an injury bothering him - but it was surprising how easy it was for Andy.
Federer has played a major part in many of Murray's disappointments in recent years, which means Andy would have enjoyed the win even more. But that's not to say I'd make Murray favourite for the US Open.
Djokovic was disappointing at the Olympics but is starting to play well again. Rafa is just a big question mark while Federer's performance in London also sees doubt surrounding him. I think maybe he was just trying too hard to win the gold medal: Olympics singles gold is, after all, the only thing he's never won. If that is all it was, then he still must start as favourite for the US Open, but he was very subdued in that final.
All this means that this just might be the Grand Slam where we have a winner away from the top four. I can't tell you who that will be, but Jo-Wilfried Tsonga - if he's okay after walking into that fire hydrant - or even former winner Juan Martin Del Potro could come into the mix and that's the first time we've said that for a while.