World No.79 O'Connell lost his first-round Wimbledon clash to Taylor Fritz on Wednesday and has now confirmed he will be unable to take his place on the Roland Garros clay later this month.
"I was so excited to qualify for the Olympics and am disappointed that my body is just not where it needs to be to compete on the clay," he said on Friday.
"I wish all the team the best of luck in Paris."
Chris O'Connell has withdrawn from the Olympics after picking up an injury at Wimbledon. (AP PHOTO)
Emerging 22-year-old Gadecki benefited from Australia receiving a second women's doubles quota-place and will make her Games debut alongside a childhood idol.
"It's such an individual sport ... to be part of something bigger than yourself is something that doesn't happen often," she said.
"To be able to have that opportunity is amazing. I just can't wait to soak it up.
"I've known Ajla probably since I was 16. Growing up watching her train in Brisbane during her pre-season was very special and I learned a lot from her."
Tomljanovic is Australia's only women's singles entrant, with Alex de Minaur, Alexei Popyrin and Rinky Hijikata all set to feature in the men's draw as Olympic tennis is played on clay for just the second time.
Matt Ebden and John Peers will be medal contenders in men's doubles while Ellen Perez and Daria Saville will also combine.
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