The South American frontman's contract with the Brazilians is coming to an end in June 2018, but according to a source at Chloorkop, the management is looking into releasing Castro to his suitors as early as next year.
Castro hasn't featured for the Tshwane giants since October after it became clear that he wants out of the club due to a broken relationship between him and coach Pitso Mosimane.
Mosimane recently confirmed that Castro is on his way out of the club, and he's already looking to replace him come 2018.
The source revealed that Sundowns could decide to handle the matter the same way they did when Katlego Mphela moved to Naturena on a six-month loan before joining them permanently at the end of his loan deal in 2014.
"The management is looking into Castro's situation. He could be allowed to join the club of his choice in January, but that could be on a short-term loan deal," the source told Goal.
"We know that Chiefs are very interested, and the club is aware. They could have him before the January window closes in 2018, but of course that will depend on the agreement between the two clubs," added the source.
"If you look at it, Castro's situation is similar to that of Killer [Mphela] and if the two clubs agree, then he won't have to wait for his contract to expire in June," the source concluded.
Chiefs are desperate to acquire a top striker this season, and it is for that reason they have left their foreign quota open as they continue to cast their net far and wide.
Sundowns on the other hand, have exhausted their foreign quota for the season, and with Ricardo Nascimento having reportedly agreed to a new deal, Castro's possible departure in January could open doors for the Brazilian defender to be registered with the PSL.