The Yokohama F. Marinos’ league winning manager signed off his emotional message ‘Boss’ as he prepared to take over at Parkhead, hours after being eliminated from the Emperor’s Cup.
Marinos returned the sentiment, paying tribute to the title-winning Australian who will replace Neil Lennon after three and a half years in Japan.
And Postecoglou said the club would remain in his family’s hearts.
"Words cannot express the feeling of gratitude I have towards everyone involved at the football club,” he said.
“From the board of directors to the staff, this special group of players, and finally the most passionate supporters in the country, everyone has given me the best support any manager could want.
“When I arrived my vision was to make Yokohama F.Marinos the most talked about team in Japan. I wanted to have success but also play football that would make everyone proud of our Football club.
“It was not an easy path we chose and there were many challenges, but we never stopped believing we could create something special. There have been many great moments, none better that our J-League Championship win in 2019. I will always remember that final game at Nissan Stadium.
“I was also proud of the excitement we gave our supporters. We played brilliant football at times and never stopped trying to improve in every area. We have had players represent the national team and others follow their dreams in Europe. We have achieved so much.”
Signing off with his nickname ‘Boss’ he concluded: "On behalf of my family I would like to thank the staff, players and all our fantastic supporters. We have missed you this last 18 months.
“I will always be part of the Marinos Family and you will always be in my family's heart. Forever F.Marinos.”
The third-placed J-League side returned the compliments, adding: “The club wish "Boss" nothing but the best on his new challenge in football manager career. He will always be part of Marinos Family.
"And last but not least, we thank him for leading and guiding the team to J-League Championship in 2019. His legacy and great achievement will forever remain with our club history.”