He has also revealed that Roger Federer's "people" were interested in taking part in the show, but ultimately his lack of actual tennis action led to him not appearing in the show.
RadioTimes.com spoke exclusively to Gay-Rees ahead of the show's launch on Netflix.
He said: "We obviously had discussions with everybody. But the thing is, when you're as big as Rafael Nadal or Novak Djokovic, apart from the fact that some of them have got their own projects happening already, which pre-existed ours, it's hard to really corral it.
"The younger players have more to gain from being in here and, personally, I think they're at more interesting points in their stories because when those four players have fundamentally dominated a sport maybe more than any other sport I can think about, everyone else has been sort of living in their shadow.
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"From very early on, we identified the idea of the next generation, it was never meant to be the Nadal-Djokovic show. It was never going to be that. Practically and logistically, it was never going to be that, and that was never our intention.
"We would happily have engaged with them a little bit more, but it became pretty clear, pretty quickly that wasn't the route we were going to take."
Rees-Gay added: "Roger Federer's people were really into it and they represent other players that we were talking to.
"He wasn't really playing tennis for a start. And Coco Gauff, for example, is a really good young player that we were keen to engage with, but she's very young so there was a degree of protection around her, which is totally understandable.
"If Break Point carries on, maybe she'll be in it going forward. It's all a pretty fluid conversation."
Break Point is streaming now on Netflix. Sign up for Netflix from £6.99 a month. Netflix is also available on Sky Glass and Virgin Media Stream.
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