^^^ Agreed with the above. There's nothing with showing a sore loser face after a loss. Give me that over all smiles any day of the week. It's so odd to see fans criticizing this. Do we accept that players are pissed when they lose? I would assume yes. So why do we want them to put on a happy face? Then when someone like Nadal acts like he has to play at his best every match to stand a chance people accuse him of being fake (which he is in this instance), yet we're demanding that players BE fake after they lose. I've yet to see a sport where fans want players to act exactly like they for them to act in every little instance, and give such conflicting opinions about it too. Jesus, just let them play and compete...
Also, regarding the "at his best thing," it's an abstract concept. Realistically, if any of the top 10 players in the world play a full match at their absolute best, they're not losing. Now apply that to the top 4, 3 of whom happen to be all time greats, and you get something even worse.
Let's actually apply it with concrete examples: Roger Federer.
Playing at his best means that Fed is: Serving very well to hit aces, cheap points, and set up one-two punches. Hitting forehand winners almost at will, using his backhand to spread the court and construct the points, breaking rhythm with the slice, gliding effortlessly around the court, have great success at the net, neutralize points on the return of serve, and turn defense into attack when need be.
Uh, if he's playing like this, how the hell is he going to lose?
Now let's apply the same to Nadal. Playing at his best means: Moving better than anyone in history. Dominating points with the forehand. Running opponents around the court with the forehand. Firing off huge inside out winners. Flattening out the backhand cross court with great power. Tracking down impossible balls and putting them back with interest. Hitting unreal passing shots. Neutralizing points with the return. Serving effectively to set up points and get a forehand on the next shot + free points. Make almost no unforced errors, ever. Dominate your opponent physically. Outlast your opponent. Win all the big points.
Again, how on earth do you beat that?
Now, let's try to apply BOTH at the same time when Federer and Nadal play each other. What do you notice? They're incompatible. Because if Federer is hitting forehand winners at will, Nadal isn't dictating with the forehand. Likewise, if Nadal is tracking down impossible balls, Federer isn't hitting forehand winners at will. If Nadal gets on top of the point after serving effectively, Federer isn't playing first strike tennis.
So one player being at his best automatically means the other one IS NOT. What can and often does happen (not necessarily in Fedal matches, but in general), is that two players take turns playing great tennis during a match, and it really boils down to what the other guy does when someone is playing his best, who can sustain it for longer, who makes crucial adjustments, etc... Because guess what, if one of these players is at his best for an entire match, it will be a blowout. We've seen it in Nadal/Federer matches, in Djokovic/Nadal matches, Nadal/Murray matches, etc...
What often happens is say, for example, Federer plays a great first set against Nadal and wins it. Then Nadal makes small adjustments that make Federer start going for more, missing more, etc... Suddenly, Federer is no longer playing at his best and people go: See, when he did play his best, Nadal stood no chance. Well, duh, nobody does. But it's not as simple as "he couldn't maintain it." The other player does something to bring his level down. There are so many ways to win a tennis match.