The evergreen 42-year-old Tampines Rovers' player delighted the 837 fans at the Jurong West Stadium by playing a match-winning role on Wednesday evening.
The opener came just seven minutes after kick off, when Qiu Li's inch-perfect cross from the left was met by Duric, who headed it into the net.
Riding on the momentum, the Lions extended the lead fourteen minutes later. A through-ball towards Khairul Nizam, who was in an offside position, was allowed to run Into the path of Duric who slammed it past Hong Kong goalkeeper Yapp Hung Fai to score his second.
Both sides then made a host of changes in the second half, with Singapore head coach Radojko Avramovic handing out debuts to Courts Young Lions youngsters Shahfiq Ghani and Nazrul Ahmad Nazari alongside Jufri Taha, who started the game.
The Lions were rarely threatened throughout and held on to start off their preparations for the AFF Suzuki Cup on the right note.
Speaking at the post match press conference, Hong Kong head coach Ernest Merrick felt that Singapore did well.
"Singapore were sharper to the ball, they were more competitive than we were and I thought that Duric were going to make our center backs sleep with the lights on tonight," he commented.
The Australian native added: "He made life for us very difficult for us in the first half. Overall it was a fair result, 2-0 to Singapore."
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He also singled out Mustafic Fahrudin as the other player who stood out in the game.
Singapore coach Radojko Avramovic felt that his team's first half dominance helped them on their way to the win and was happy with the free-flowing attacking football displayed by his team.
The Serbian told the assembled journalists: "First half, we controlled the game. Generally, we could have scored a few more goals and there are a few more things we can improve on, which would come with a few more games under our belt."
"I think this team can do even better for that part, but there were some good passing, some good combinations, especially the chance Qiu Li had when he hit the bar. That was some really beautiful football."
Avramovic also mentioned that the three debutants did well but need more international experience under their belt.