Director of rugby Mark Hammett has left Cardiff Blues after only six months of a three-year contract.
Blues said in a statement they are disappointed he asked to leave for "personal reasons".
Former All Blacks hooker Hammett, 42, was appointed for 2014-15, replacing former Wales international Phil Davies.
Blues have won only four of 15 matches in the Pro12 since his appointment, losing lost 40-24 to Treviso on Friday to leave them are 10th in the table.
Assistant coaches Paul John and Dale McIntosh have been put in temporary charge with Blues struggling to qualify for the top tier of Europe competition next season.
|Possible successors to Hammett:|
|Mike Rayer - Former Wales and Cardiff full-back now at BedfordDanny Wilson - Currently assistant coach at BristolGeraint John - Former Cardiff fly-half, now coach of Australia sevensRob Howley - Wales attack coach and former Blues scrum-halfDale McIntosh - Defence coach under Mark HammettPaul John - Backs coach under Mark Hammett|
John and McIntosh did likewise when Davies left in March 2014.
Blues will seek a permanent successor to Hammett, who said: "It was always my intention to bring success to the region over the full length of my contract.
"However, I must put my family first and therefore it is with regret that I am leaving the role.
"I'd like thank [backer] Peter Thomas and the board of directors for their support in allowing me to return home as soon as possible.
"I would also like to pay tribute to the amazing fans at Cardiff Blues for their backing throughout my time here and I hope they understand the difficult decision I have now made.
"I wish the region every success and look forward to seeing the team develop in the coming years.
"Finally, I'd like to make a personal thank you to the players and staff for their hard work and dedication."
Blues chief executive Richard Holland said: "We were naturally very disappointed and surprised when Mark informed us of his decision.
|Cardiff Blues coaches|
|Dai Young: 2002-2011|
|Justin Burnell and Gareth Baber: 2011-2012 (temporary)|
|Phil Davies: 2012-March 2014|
|Paul John and Dale McIntosh: March-June 2014|
|Mark Hammett: August 2014-2015|
"However, we fully understand the personal reasons he has given and he has our full support.
"We appointed Mark last summer as part of a long-term vision for Cardiff Blues.
"He has worked tirelessly in the role since his arrival in Wales and we always felt Mark was the right man to take us forward, right up until his decision to leave.
"Mark has made a number of positive changes that will benefit our region for years to come. He leaves us in a stronger position than when he arrived."