The story of Thiem's R16 match was his impressive winning % off his first serves. I think he barely lost 4 or 5 points in the whole match on first serve. While Rafa was winning continuously, none of his opponents so far was having a decent serve that stings (I am not even talking about Isner, Raonic, Karlovic variety here). That was helping Rafa quite a bit. Also, keep in mind that Thiem can go toe to toe on ground strokes with Rafa.So, contrary to popular opinion, I expect Rafa to struggle in this match quite a bit. But, I also expect Rafa to pull it off in four close sets.