The Brazilians tabled a formal offer for the winger's services earlier this week, and Amakhosi confirmed that they were still considering it.
Now, with Lebese clearly unsettled at the club, the technical team saw the need not include him in their plans for the new season which kicks off on Friday.
The 28-year-old was then ordered to train with the club's U19 team until his future is resolved.
Sundowns are pushing to sign Lebese before Friday as they look to register him for the knockout stages of the 2017 Caf Champions League. The deadline for registering additional players with Caf is on Friday.
Recent reports suggest Chiefs want at least a player plus cash in order for Lebese move to Chloorkop ahead of the new campaign.
Sundowns have reportedly offered Mzikayise Mashaba to try and sweeten the deal, but Chiefs are yet to make a decision.