The Celtic managerial target, who is believed to have agreed terms to move to Parkhead, saw his team taken to extra-time in the Emperor’s Cup clash with fourth division Honda FC.
But the Nissan Stadium was stunned by the visitors’ 28th minute penalty converted by Honda goalkeeper Yuki Kusumoto – and smashed high into the net for a lead they held into the second half.
Marinos levelled and then took the lead in extra-time, only to be pegged back and then defeated in a penalty shoot-out 5-3.
Defeat comes as a huge shock to the 2019 J-League champions who are currently third in the first-tier league, but have five games in hand on leaders Kawasaki Frontale who were also taken to penalties in their cup clash by tier three side Nagano Parceiro. The league leaders edged through 4-3.
Postecoglou was not quite as fortunate and on the end of a giant-killing in what is expected to be his final match in charge of the Yokohama club he led to the J-League title two years ago.
Weekend reports suggested his move to Celtic would be confirmed early this week, but the former Australian national team manager dodged questions over his expected move to Scotland, insisting he is fully focussed on the J-League side’s next fixtures, including today’s cup clash with the fourth-tier side.
Previously Postecoglou led Australia to two successful World Cup qualifications and an Asian Cup triumph in 2015. He is now the leading contender for the Parkhead role after a deal for Eddie Howe collapsed.