John Wooden coached UCLA to 10 NCAA basketball titles in 12 seasons.  This is indeed impressive.

Advantage Rafa – Rafa played while Wooden coached.  Perhaps, Wooden should be compared to uncle Toni Nadal.  Similar points can be made in terms of compairing Rafa to Phil Jackson and Red Auerbach.  Playing and coaching are different.

Tom Brady has won 6 Super Bowls from 2002-2019

This is very hard to compare: a team sport with violent collisions vs. an individual that is physically taxing but not terribly violent.

Edwin Moses won 122 consecutive races in the 400 M hurdles over a decade.

This is easier to compare, and Moses holds up quite well.  Going undefeated for a decade is insane.  There are different events and distances in track, but there are different surfaces and types of tournaments in tennis.

Larry Holmes held at least one of the three recognized world heavyweight titles in boxing from 1978-1985.

Floyd Mayweather is 50-0 as a professional fighter fighting in multiple weight classes.

Lebron James reached 8 consecutive NBA finals with two different teams.

Michael Phelps and Usain Bolt each had a great deal of success across multiple Olympic games.

Rafael Nadal is easily a Hall of Fame tennis player without any of his Roland Garros results.  He has 3 US Open titles, 2 Wimbledon titles, and 1 Australian Open title plus a gold medal in singles (2008) and doubles (2016).  His results in Paris are so far beyond what any could realistically have predicted that Rafa is somewhere in the sports pantheon of greatness.