He looks unplayable.
Nadal isn't at his very best, but I put some of that down to not knowing how to approach Wawrinka, he can return with pace from anywhere on the court & that single handed backhand gives him a bit more breathing space as he's not pushed across the court with his momentum.
I often think how I'd approach playing someone, but I'd not have a clue how to play against him.
All that said I expect Nadal to make a comeback at some point, as unlikely as it looks currently.