The former Wimbledon champion says that he was told by one tour player on Monday that "tennis in Aus is gonna die" if there's not a complete change in the tennis authorities' priorities.
While Alex de Minaur was left enthusing at the French Open in Paris on Monday about news of Abdo's appointment, hours after the 47-year-old official's shock resignation as the NRL chief executive, former Wimbledon champion Cash was offering a far more downbeat and pointed message on Instagram.
Abdo has been much lauded for his influence in rugby league, with Australian Rugby League Commission chair Peter V'landys suggesting he'd been so influential that only "Superman and Jesus added together" could possibly replace him.
On hearing the news of the successor to long-serving TA boss Craig Tiley, de Minaur, Australia's No.1 tennis man and a rugby league lover, said he was "excited to see what the vision is going to be" for the sport that Abdo would bring.
But Cash sounded much more sceptical in his post, asking: "Can an NRL commercial exec fix the heart and soul of Oz tennis? I wish Andrew the best of luck.
"Has he been drawn into the glitz and glamour of the AO beer sales and one point tennis matches, or is he gonna work on saving the heart and soul of Australian Tennis?
"After all, there are 49 other weeks to the year. I keep hearing participation is up? Compared to when?? Reality is, club tennis and competition has been dying for decades!! Local coaches are exhausted and fed up, clubs are going broke, junior results are the worst in history.
"Priorities of @tennisaustralia need a complete 180 turnaround, or as one tour player told me today, "tennis in Aus is gonna die."
For Aussie players at Roland Garros, the news came as a big surprise, with a couple telling AAP they didn't know who Abdo was.
"It's something that's come overnight. I don't know him personally. I'm sure I would love to get to know him and learn a little bit more about what he's keen to do or what his vision is for Tennis Australia," said de Minaur, a huge NSW fan who always used the 'Blue Wall' as his mantra as a young player.
"Of course, we had Craig for a long time, who I thought did an incredible job. Tennis Australia is a really strong federation. In the whole performance phase, we've done a pretty good job over the last couple of years, about showing strength in numbers, especially in the men's side in the top 100.
"There's definitely places we can grow, and I'm excited to see what the vision is going to be."
Asked by AAP about what he felt Abdo might bring to Australian tennis, Rinky Hijikata, one of six Australian men in the top 100, said: "My guess is probably as good as yours.
"From what I've heard, is he's done well with the NRL, and I'm a Parramatta Eels supporter, so I follow the NRL, but I haven't paid too much attention to what he's done in the league.
He added with a laugh: "But the Eels are playing in Las Vegas next year, so maybe I'll see if maybe he can get me a few tickets for next year's game!"
