It's not the answer to all of his losses, but it's rather hilarious that some people still find it unbelievable that he was carrying injury in that 2009 RG match. There is a lot more to argue for it than against it. Everyone agrees that Soderling played a great match that day. No doubt about it, but Nadal-detractors can't seem to accept that injury could have played a part.
As the years go by, the very fact that the best haven't been able to beat him at RG should be one indicator. He's like 118-2 in Bo5 on clay. Djokovic couldn't beat him until his worst year, (2015,) and yet Soderling was able to do it when Rafa was 22. Even when Rafa had crushed Soderling 1 and love just a few weeks prior. Even though Nadal had been carrying knee tendinitis for some time, and even though he had to withdraw from Wimbledon, which he was defending, and take 2+ months off after that match.
The best is that Djokovic fans have no problem accepting when he withdraws due to injury, and comes straight back to win tournaments. (Cincy '11/USO '11, as an example.) And Federer fans have no problem insisting that he lost due to injury, even without withdrawing, but fair excuse, (USO '17 and '19, and Canada '17 come to mind.) However, if Rafa loses (RG '09) or withdraws due to injury (USO '18 has been brought up recently,) it's all just made up BS. If folks don't see that as wildly contradictory, I don't know what.
PS: And if one more person tells me that "yes, but Rafa was running around like the energizer bunny in that RG match," I will come through my computer at them. Playing through pain means nothing, apparently, unless it's Roger.