It looks like he could be out of the game in a couple of years. Playing singles on the tour for an entire career isn't easy and it's not for everyone.
It's very strange how he looks so engaged for Davis Cup play and then so lackluster for tour play. Now this was a Challenger level event so that might explain it somewhat, but then why even sign up to play if your heart isn't in it?
Nishioka acted like an idiot throughout the entire match and ends up winning. Really bad loss for Felix (56 unforced errors).
So weird how Felix and Dennis can raise their level of play for Davis Cup and beat anyone but come out so flat and uninspired in tour events. I admire that they bring it when playing for the flag but they are both doing a disservice to their personal careers not being able to bring it on tour events.
Just a day/night of upsets in Tokyo as in addition to Felix losing, Oikos was eliminated by Alex Michelsen in three sets and top seed Taylor Fritz was beaten by Arthur Fils.