SYDNEY Swans midfielder Isaac Heeney has suffered a broken jaw while on holiday in Hong Kong after an unprovoked attack. 

The Swans confirmed on Sunday evening that the young star was struck from behind when trying to enter a cab and is now on his way back to Australia. 

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The 19-year-old, who finished fourth in the 2015 NAB AFL Rising Star, is expected to be available for day one of pre-season training. 

"The Sydney Swans are aware Isaac Heeney was involved in an unprovoked attack while in Hong Kong with teammates on Saturday morning," the Swans said in a statement.

"The 19-year-old was trying to enter a cab when he was struck from behind.

"After being taken to the closest medical facility, it was detected that Heeney had suffered a fractured jaw in the attack."

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One of the brightest young stars in the game, Heeney was recruited as a Swans Academy selection with pick No.18 in 2014 and played 14 games in his debut season.