The New Zealand international midfielder will link up with former Mariners boss Graham Arnold in the J.League with Bernie Ibini set to return to Gosford from Shanghai East Asia (SIPG).
Mariners chief Mike Charlesworth said: "I think Michael will be following Arnie to Japan. Terms have been agreed though I am not sure whether they have been signed off on yet.
"But it looks as though the move will go ahead. It will be a loan deal for the Japanese season and the reality is that could lead to us receiving a transfer fee for him if he does well, either from Vegalta or perhaps another overseas club.
"Michael wants to go and experience the J.League and from a positive point of view for us, it's yet another player that we have managed to help develop their career.
"There is no other A-League club that comes anywhere near our level of success in terms of producing players that move onto bigger leagues.
"Unfortunately, our business model is one where we have to sell players. That's just the way it is – and if that means putting somebody like Michael in the shop window for a few months (in Japan) then so be it."
As for 21-year old striker Ibini, who joined Shanghai in June, Charlesworth added: "We are hopeful that Bernie will be back with us on loan.
"We were sad to lose him in the first place and it would be good to see him return also during the transfer window."
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