The thing that gets me about this idea that Wawrinka is suddenly a huge threat to Nadal is this:
A year ago, nobody would have given Stan a chance. So what changed? If it's the fact that Wawrinka won a slam, matured, and has more belief, then sure. I'm sure that will raise his chances somewhat (just how much is debatable, since he still has a lot to overcome given who his opponent is and the nature of that match-up). If it's because he beat Nadal in the final and it would give him even more belief, then again, fair enough.
But the argument often raised is THE WAY Wawrinka beat Nadal. To me, that's the problem. Wawrinka had an all-time best performance. As in, he probably played the best tennis match of his career. When ANY top 15 player plays the best match of his career, he is going to win. Period. No questions asked.
You really think if Berdych has his best ever performance against Nadal, he wouldn't win? These players aren't separated by THAT much.
My point? You're not going to have an all-time great performance every day. And Wawrinka's 11 previous meetings with Nadal proved that anything less wasn't even enough to win a set. That's pretty important right there, and highlights how difficult the match-up is for Stan.
If I show you highlights of Tsonga's win over Nadal at the 2008 AO and you weren't aware of what happened afterwards, you'd think Nadal would never beat Tsonga in a match, ever. Of course, reality is different because Tsonga is not going to play like that every time, and anything less won't cut it.
There's a reason the really great players are who they are: They are able to beat each other without playing that great. Think of it this way: How many times have we vociferously argued about how say, Federer played so poorly because Nadal didn't even need to play his best to beat him. Or why Djokovic played poorly because Murray didn't have to do much to beat him, etc...
But do you ever say, Nishikori didn't have to play his best to beat Djokovic? Or Tsonga didn't have to play his best to beat Federer? No. Because most times, for these "lesser" players to have a chance against the truly great players, they HAVE to play their best, at least in majors. To me, this is actually not a good proposition: "play your best to have a chance." That doesn't sound like the odds are in your favor.
The point is, these are extremely "situational" events that don't happen often. As off now, Wawrinka's level at the AO is not the rule. Because he hadn't produced it consistently before or since. What he has done, is play very well for the better part of his career, and yet still came up short against these guys. That's far more telling to me.
...and then there's the fact that Nadal injured his back in that match :snigger