Mhlongo, a former Orlando Pirates assistant coach, started to encounter problems with the Mpumalanga-based side after Sammy Troughton took over as the club's technical director late last year.
"Yes, it happened (Mhlongo's exit) last year already," Nyambi told KickOff.com.
"Before they went to Real Kings. When they lost to Real Kings he was no longer there. There was a mutual agreement for them to part ways.
"It was clear that there were some advisers that were coming from different angles and they were complicating the effectiveness of the contract that was signed then with the owner of the team.
"So we decided that if ever we change conditions of the employment of course linked with the issue that we have discussed, which is clearly unbearable to be effective and produce expected results.
"So from that day we agreed that it's better to have good relations and part ways."
Asked what is next for 'Mayanga', Nyambi said: "No, we are working on something. At an appropriate time we will make the necessary announcement."
Sporting refused to comment on the matter.