Parks, who had originally given himself a year to see if wheelchair tennis was feasible, is proud but modest about his own role 50 years on.
“I was the head of the organisation, I was the first player to really play the game but it’s hard for me to say Brad, you invented wheelchair tennis, but you know I was part of it,” he said, pointing to others like Minnebraker.
Today’s players, though, do not hold back.
“I think I’m in awe. Absolute awe,” said Britain’s 34-time Grand Slam champion Alfie Hewett.
“It [wheelchair tennis] is not about accolades and the external things. It’s actually just the life it’s given me and the purpose that it’s given me.”
And Gordon Reid, who has won 30 Grand Slam titles, added: “It’s an incredible story and that little idea that he had 50 years ago has turned into a huge worldwide sport now. So yeah, [I’m] very thankful that he had that idea back in the day.”
So much has changed since the early days, not least the chairs which are much lighter and often feature a moulded seat that is more energy efficient for turning.
And the sport continues to grow – the wheelchair event at Wimbledon, which begins on Tuesday, offers a prize pot of more than £1m, with the winners of the men’s and women’s singles earning £82,000.
Its profile is also rising and the finals are now played on the 12,345-capacity Court One, compared to the 276-seat Court 17 that hosted the first wheelchair singles final 10 years ago.
Parks says he is “very happy to see where we’re at”.
“I’m jealous in a way but in a good way because I would have loved to have been able to play in [tournaments like Wimbledon],” he said.
But that was never what his dream was about when he set out.
“I just loved to hit tennis balls, and I wanted to share the feeling of hitting a tennis ball from a wheelchair,” he said.
“The thing that I feel really, really good about is that I really wanted other people to be tennis players.
“I used to get disappointed when I thought that everybody was wheelchair basketball players. Tennis was not their main thing. And today I feel like tennis really stands on its own and they’re tennis players. They just happen to be in a wheelchair.”