Departing Central Coast coach Graham Arnold has apologised to fans for leaving the A-League in the manner he did.
Arnold suddenly quit the defending champions last week to sign a two-year deal with J-League club Vegalta Sendai, making him the first Australian to coach top-flight football in Asia.
The 50-year-old, who returned from a five-day trip to Japan on Tuesday, said it all happened in the space of 24 hours.
"It's very sad to leave the Mariners and I apologise to the supporters and everyone for the way I left because it happened so quickly," he said on Thursday.
"I will always cherish this club enormously. I will be back one day.
"I just felt that the timing of this move was perfect.
"I went over there (to Japan) for five days and I could feel the intensity coming back. I could feel the desire of wanting to be successful and prove myself - again - overseas."
Arnold said while he would have been very happy to see out his three-year contract - which included a clause to leave for an overseas posting - he needed a new challenge after last season's grand final triumph.
The ex-Socceroos mentor is yet to speak to his players about the move, trying not to distract them from Saturday's clash with Perth Glory.
"Last week they were probably in a little bit of shock when it came out that I'm leaving. They didn't need me to disrupt their week this week, so I'll approach them and address them over time," he said.
"But since I've been at the Mariners, I've let 10 or 11 players go and sold them overseas and helped them move on in their careers.
"I know the players might be disappointed but they also know it's reality and it's now my turn."
Arnold has pledged to watch every one of the Mariners' home matches over the next seven weeks before he moves to Sendai, and has offered his support to successor Phil Moss and Central Coast's National Youth League coach Patrick Zwaanswijk.
However he is confident Moss, formerly an assistant, will do well in the new role.
"Hopefully, he's learnt a lot from me over the last three years," he said.
"He's got a wonderful stable group of senior players that are very good for him to lean on and he's got some quality youngsters.
"I know that they'll be up there towards the end of the season ... and I'm sure the Mariners will be in very good hands."