Celtic manager Angelos Postecoglou celebrates with the league trophy after winning the Scottish Premiership, at Celtic Park, Glasgow, Scotland, Saturday, May 27, 2023. Photo: AP
The 57-year-old Postecoglou is widely expected to leave Celtic and be named boss of Premier League Spurs, although there is yet to be an official announcement.
The move has been met with scepticism from a section of Spurs fans who wanted a higher-profile appointment than the Australian.
Arnold knows Postecoglou well, having worked with him at the Australian Under-20 side, and said: "Just working with him you could see the obsession of football, he had that mentality of where he wanted to go -- and that was to the top.
"He is totally obsessed with the game, it is his life.
"Ange has always been someone who is so determined to prove the doubters wrong."
Arnold called Postecoglou a friend as well as a former rival in Australian football, and added: "Going to Tottenham is a great job for him and I think he will kill it."
Arnold said that Postecoglou, who managed the Socceroos from 2013 to 2017 and has won league titles in three different countries, stood out because he was both a coach and a manager.
"A lot of managers are managers, they are not coaches as well, but he has that dual role of coach as well as manager.
"He knows man-management and how to motivate people."
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