This out is 10 cm at most. It's not like he missed it by 50 cm. A player can't know that if he is standing ON THE OTHER SIDE OF THE COURT. I mean, they don't even see where the ball lands. I played tennis in the past, I know what I'm saying.
Yes, you can. It may sound strange, but you have an extremely good feeling about the length of shots when you play a lot of tennis.
I never said he missed by 50 cm, did I? I said a player knows when he hits 10-15 cm out. Because he does.
Rafa's shot is perhaps 7-8 cm long (if the line is 5 cm, which is common on clay courts. Some baselines are wider, even on clay).
I have never said Rafa should give the point to Goffin. Of course not. In tennis, even without umpire, you don't get to make decisions regarding a shot that is not on your half of the court.
In a situation without an umpire, Goffin would call it out, and Rafa would say OK.