"T20 leagues are a threat for international cricket. The power of the leagues are growing year by year and obviously in the beginning there might be just 2 leagues around the world and now its becoming 4,5, 6,7 leagues in a year. The leagues are just getting stronger," he said in a virtual media interaction ahead of the PSL.
"I think its important that in future you try and see how its possible both can co-exist because it it becomes a choice moving forward into the future then it can be a real threat for the international game."
Du Plessis, who will play for Peshawar Zalmi in the PSL, which resumes here on June 9 after COVID-forced postponement, said if the guardians of the game don't take corrective steps now, international cricket runs the risk of losing out to domestic leagues in future, just like soccer.
"That is a huge challenge. May be in 10 years time cricket will almost be like soccer where you have your world events and in between you have these leagues around the world where players can play," the veteran South African batsman said.
Citing the example of West Indies players like Chris Gayle, Dwayne Bravo among others, Du Plessis said many current players might opt to become freelance cricketers going forward, which would be a big loss for their respective national teams.
"If I take someone like myself you go and play 2 or 3 or 4 leagues around the world but I can't predict the future. There are more and more players...(who want to play in T20 Leagues).
"West Indies probably is the first team that started doing it. All of their guys moved away from international team to the T20 domestic circuit. So the West Indian team lost a lot of their key players. It's starting to happen with South Africa also," he said.