system
Given the following post, respond as if you're commenting on Reddit:
human
CMV: John McEnroe isn't sexist when saying Serena isn't one of the best tennis players of all time.

A couple months ago in an NPR interview John McEnroe caught major heat from the MSM for what was said about Serena. Here is the interview transcripts. 

"Garcia-Navarro: We're talking about male players but there is of course wonderful female players. Let's talk about Serena Williams. You say she is the best female player in the world in the book.

McEnroe: Best female player ever — no question.

Garcia-Navarro: Some wouldn't qualify it, some would say she's the best player in the world. Why qualify it?

McEnroe: Oh! Uh, she's not, you mean, the best player in the world, period?

Garcia-Navarro: Yeah, the best tennis player in the world. You know, why say female player?

McEnroe: Well because if she was in, if she played the men's circuit she'd be like 700 in the world."

Is what he said wrong? Obviously we are talking skill wise and not about success of the careers.
gpt
This depends on how you want to define "best". 

The one that McEnroe is using is "who will beat who in a match". In this way McEnroe is entirely correct. 

However another way to define best would be who has the greatest technical aptitude. This becomes a bit more subjective but there is some quantification to it. Usually by people within the sport/field assessing it and the dominance of the person against those with the same bracket as them. 

Take boxing for example. Many might say someone from the featherweight division is actually the better boxer but still acknowledge that they'd be destroyed by the worse boxer whose a heavy weight. 

Who wins is usually a combination between physical condition and skill. When talking about whose the "best" some people are referring solely to skill while others like McEnroe are are taking both into consideration.