The Japan-based attacker was back in the national team fold for the first time since 2013 when the Australia boss assessed the merits of 30 players during a training camp in Turkey earlier this month.
And Duke, 27, saw a coach who has refined and honed his skill set since they were first together at the Central Coast Mariners back in 2010, including his ability to burrow into the psyche of his players and invoke a fierce loyalty, commitment and improvement.
“You can see already he’s given a lot of the Socceroos boys (especially the younger ones) a measure of confidence with his mentoring,” Duke said.
“When it comes to man-management he’s one of the best there is.
“Of course it’s vital what he does regarding what happens on the pitch but what he can accomplish off it can’t be under-estimated.
“He creates an environment and an atmosphere which mentally plays a huge part, more than people realise.
“He’s done that at previous clubs and it’s a big part of his success.
“There’s a lot of excitement about what he might bring and people just want to do well for him to do well for the country.
“He’s had his own coach’s whisperer (Bradley Charles Stubbs) when he was at Sydney FC and he’s stepped things up in that area and is helping more and more with his success.”
Whilst Ange Postecoglou was intentionally distant with his players - to the point that some saw it as a negative - Arnold is open and available.
“He’s a coach who takes a lot of his own time to talk to you and teach you certain things,” added Duke.
“A lot of coaches don’t do that and it’s not something I’ve experienced in Japan, and I’ve had four coaches here.
“Arnie will pull you aside, and if he sees you’re struggling or if he wants a bit more out of you, he has a way of getting that 10 percent extra from you.
“Whether it’s scoring a goal, doing better defensively, whatever it is, he’ll get that much more out of you.
“That’s his little gift in terms of man management.
“Back in the Mariners days that’s what he did for me personally.
“When I was coming off the bench, he’d say ‘you’re going to come on and score two goals’.
“It just gives you that confidence and is a very under-rated factor in football.”
A regular fixture for Shimizu S-Pulse over the past four seasons, Duke thought he did himself “no harm” in terms of a possible call-up for October’s friendly in Kuwait during the camp, and January’s AFC Asian Cup beyond that.
“I think the camp was as much about judging players as getting them together to connect and put his ideas forward,” he added.
“I didn’t feel out of place and felt I did myself no harm with possible selections and things like that.
“Arnie understands that players need an adjustment period to his style of play and that was what it was a lot about.”
Duke believes Arnold won’t change too much in the defensive formation he inherited from Bert van Marwijk.
But flexibility will be far more apparent in the final third, where he might unleash a number rotations and formations.
“I think you’ll see a lot of versatility there and he definitely does have the players to mix it up a bit in those areas,” he added.
“He think he’ll be looking to bring out the best in an attacking sense from his wingers and his number 10 because we didn’t score goals from open play at the World Cup, and not many either in some of the qualifiers.
“That’s certainly something he’s looking to rectify.”
