By the way, he just won the first round match against Cerundolo 6-4, 6-3 and was looking in good form too.
Nothing has happened to Nadal, he's won the first two sets against Cerundolo and we're heading into the third set now.
It's just there is some concern over his fitness, with the injury he's been managing, and after he effectively won the French Open on one foot, with no feeling in the other. The pre-Wimbledon surgery apparently went well, which is why he's playing now... but it's difficult to tell whether his body will be able to hold up for seven matches in a fortnight, which is what it takes to win the tournament. If he can stay fit, then he's certainly one of the favourites to win the thing... but we just don't know for sure whether he'll hold up.