Adelaide United defender Cavallo made the announcement in a video and open letter on social media on Wednesday.

The news is a historic moment for sporting community and one Cavallo hopes will help others find the courage to follow in his steps.

"I want to help change this," he said. "I want to show that everyone is welcome in the game of football and deserves the right to be their authentic self.

"It is astonishing to know that there are currently no gay professional footballers who are out and actively playing, not only in Australia, but around the world. 

"Hopefully this will change in the near future."

Cavallo's announcement was met with widespread supporting, with Pique praising the 21-year-old for making the public announcement.

"I don't have the pleasure to know you personally, but I want to thank you for this step that you take," Pique posted on Twitter. 

"The world of football is far behind and you are helping us move forward."

Pique's former Barca team-mate and current Atletico Madrid loanee Antoine Griezmann said: "Proud of you @JoshuaCavallo".

Barca was one of a number of teams to commend Cavallo, posting: "THANK YOU, @JoshuaCavallo for taking a huge step forward! 

"Your courage contributes to normalizing diversity in the world of sports."

Premier League side Arsenal tweeted: "Thank you @JoshuaCavallo for your strength and bravery...

"You are an inspiration to millions. Everyone deserves the right to be themselves."

Several other top-flight players have previously come out as gay once their professional playing careers were over, including former Aston Villa player Thomas Hitzlsperger.

Former Newcastle Jets player Andy Brennan came out while playing in a lower tier and is now plying his trade for semi-professional side Hume City.