A number of things here...
Soderling was not a nobody. Even at that time he was known as a nearly man who on his day could beat anyone. If you're specifically referring to clay, then perhaps I can give a bit more leeway, I think we had all assumed hard courts were his strongest surface.
I can understand why Rafa fans found the whole "Rafa couldn't play Wimbledon because of injury" such a compelling explanation for his loss at RG. But I have a major problem with that. I will never... let me capitalise that...NEVER!!! concede that Rafa was impaired in that match. I have watched the match several times (one thing Rafa fans don't consider is the fact that we Fed fans watch this match a lot, if you're like us, you don't go back to watch your guys losses, so I wager we've actually watched the match more than you!) and I maintain that Rafa's movement was fine. What was different was that he was hitting short balls against a guy who was punishing him. Soderling was able to hit through the courts like no one I can remember. It wasn't quite as cold and damp as the next year when he crushed Roger, but the ingredients were all there. You might want to console yourself that there was an injury. You might want to console yourself that his skipping Wimbledon due to injury confirmed that. But that makes no sense whatsoever. A few years ago Roger injured himself bathing his child. It wasn't anything to do with tennis, these things happen. In summary I do not accept the linkage of his missing Wimbledon with his loss to Soderling, that's circumstantial at best, and frankly fails the eye test of the match itself.
I'm frankly shocked at how hard-headed you're willing to be that Nadal was not at all injured during RG 2009, given evidence to the contrary. I've taken note that you've called me an excuse-maker for Nadal, (for which I take more than a bit of umbrage,) but I'll risk it again with a response. But first I'll say, again, that any reasonable tennis fan has acknowledged that Soderling played exceptionally well that day, and had a strategy for Nadal that worked. (One note: Roger and Novak had more than a few chances to do the same and couldn't manage it, until 2015, when Rafa was having a very bad year. Surely they're better than Soderling. If the key to beating Nadal at RG had been found, why didn't they employ it? And why couldn't Soderling do it again in the final a year later? I would think that would give you some pause.) Also, I don't see how you don't make any connection between Rafa being injured during RG, and skipping Queens and Wimbledon (both of which he was defending.) He didn't get injured bathing his child or fishing in Mallorca. When do you think he got so injured that he couldn't defend his whole grass season? Or maybe you
do think that he just slipped on his boat.
I did watch the highlights reel that someone (El Dude?) posted, and even there you can see Rafa giving up on points that he never would have before. Also, he was not hitting nearly as short as in his nadir year of 2015. Again I'll say that Soderling was stellar, but Rafa was off a step, at times. And take
@brokenshoelace's analysis of it into account. I think it's valuable.
For the reasonable observer, there was a march towards the end of Nadal's knees that had begun the year before. You saw his knees strapped even at Wimbledon '08. He skipped the 2008 DC final v. Argentina due to left knee. You also know how his last 2 rounds at the 2009 AO went. And 2 weeks later he played Rotterdam (which I'm still angry about, in the same way of Fed fans mad at him for playing Montreal this year,) where he had a
knee issue in the final v. Murray. The SF in Madrid v. Djokovic did him no favors, and he
talked about how the knee(s) were giving out, and he was losing some advantage and confidence, since Monte Carlo. (It's in Spanish, but you can google-translate.)
You can say that Robin Soderling won that match outright, and he did, but I don't know how you can deny that Nadal's knees weren't troubling him, at least. Even Darth admits that, and he's way more of a fan boy than you. Tendonitis is progressive. Do you think that Nadal doesn't have it?
And to your point about Soderling being a "nobody." I'll defend
@brokenshoelace's saying that, in the sense that he was surely an underachiever, at that point. Only Bjorn Borg (fellow Swede) was pushing for his chances. Beating Rafa at RG was absolutely his break-through.