Looks like Novak and Thiem played one hell of a match. It also looks like Novak is having some matchup issue with austrian who is hitting the balls very hard, but also can stay patient enough which makes Novak uncomfortable, sort of like Wawrinka. Thiem really seems like he had enough of that loser shit and it's just going for it full of belief. I also don't get why some people don't like him.
While Novak has mental edge over Fed and Rafa (except at RG) he will definitely have to find ways to deal with these young guys as they keep winning against him more and more often. I think he is afraid of Thiem now in some way, because he knows he is not afraid of him and now he comes creeping in his head so he loses his confidence. It also looks like Novak is not able to stay with him with that intensity of play to push to the finish line. If he doesn't come playing lights out tennis there is going to be more of these loses in the future and in the slams too.
He needs to evaluate his game and make some adjustments and improvements before it is too late, but there are limitations to improvements no matter what you change and at the end it's all about weapons which you have and against big hitting guy like Thiem or defensive guy/counter puncher like Medvedev who can also hit big he don't have much artillery to hurt them and win comfortably. It's mostly going to be close matches going forward with decent chances of losing.
Now the battle with Fed will be so interesting, because it is best of 3 and I could see Novak losing this one even his level seems to be better at the moment than Feds, but he could be tighter. Fed should swing freely with nothing to lose. Bookies will still probably put Novak as a favourite, but so far favourites are mostly losing in London this year.