The Bulls on Monday confirmed the departure of defence coach Joey Mongalo.
This comes after Sport24 exclusively reported over the weekend that Mongalo had signed a deal to join the Sharks.
The highly-rated and sought-after coach joined the Bulls from the Lions in May 2020, adding to a formidable coaching unit that was put together by director of rugby, Jake White.
The Bulls said in a statement that Mongalo will leave them following a "mutual agreement".
"The Bulls wish Joey well on his new journey and we have no doubt that he will continue to flourish in his new role. We remain confident that he is an important part of the future of South African rugby," said Blue Bulls Company CEO, Edgar Rathbone.
"Joey has been an important member of our coaching staff since he was brought into the Bulls system by Jake White in 2020. He has played an important part in building and developing the side to what we see today. We are saddened to see him go, but we are equally proud to see him spread his wings as he further grows in becoming one of the country's coaches for the future. We wish him and his family well for the future."
Mongalo thanked the Bulls for giving him an opportunity in 2020.
"Being part of the Bulls over the past two years has been an extraordinary journey which I look back on with such joy and satisfaction. There were some great memories and special relationships that were build over the years which I will forever cherish.
"It is not often that one is afforded an opportunity of a lifetime. I could not let this one pass me by. It is definitely one I am grateful and excited about. I am equally grateful for the past two years at Loftus Versfeld and would like to express a word of gratitude to all at the Bulls - the staff under CEO Edgar Rathbone, the coaches, the players, sponsors and supporters. I wish the franchise well for the future."
In the two years at Loftus, where Mongalo played his rugby for the Bulls from the Under-20s to the Currie Cup seniors, the Bulls won two Currie Cup trophies, Super Rugby Unlocked and the Rainbow Cup domestic league - all available trophies during the pandemic.
Earlier this month, they lost to 18-13 to Stormers in the United Rugby Championship final but had upset the apple card with an away win over favourites Leinster in the semi-finals.