The Kenyan international is a free agent after he was released by the Team of Choice before the start of the 2019/20 season.
Onyango is said to have started training this week with the Soweto Giants.
According to Goal the central defender looks likely to sign for the Sea Robbers as they are in need of a central defender after they failed to sign Thulani Hlatshwayo from Bidvest Wits.
The Bafana Bafana and Wits captain signed a new deal with the Clever Boys, ending speculation about his next move.
The 25-year-old was a key player in United’s campaign last season and helped them survive relegation.
Onyango is set to reunite with his former coach Fadlu Davids, who he worked with at United before the coach joined Pirates as one of the club’s assistant coaches to coach Rulani Mokwena.
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