Nole is fine. One has to remember he is a primadonna baby and quitter. Most of these pros come from super rich families and they cry like bitches. Only Nadal has the heart of a sportsman and working class dude.
My opinion is that Nole, like Murray, just get by on their talent. Murray is a whiny bitch and a ****. Problem is he's just better than 95% of the tour so his pathetic attitude doesn't destroy his results. If you remember Nole from his teenage years, the guy was a quitter and soft as fuck. Problem is he is super talented and talent rules the day.
In reality, I think tennis is like the NBA in a lot of respects. Rule #1 is supreme talent. You can be an absolute lazy fuck and not do shit, but if you got the talent... just show up; ie, NBA players and Kyrgios.
It's like Deion said, "I could just roll out of bed and fucking cover" whereas some other less talented could put 200% into the craft and he wouldn't be 1/100th the talent of Deion. (Don't get me wrong. A lot of these guys are true professionals... but just calling out the other real side of the business.)