The Sydney Swans are expecting to miss star Isaac Heeney for up to a month after the gun forward broke his hand in the Swans' thrilling three-point win over Essendon.

Heeney started the game brightly, until he was seen grimacing and nursing his right hand as he made his way from the field early in the second quarter. He went straight down to the rooms for treatment.

The bad news was confirmed when medical substitute James Bell entered the game just minutes later, and when Heeney returned to the bench after half-time with his hand wrapped in ice. 

"It's just terrible luck for him. He's one of our best preparers, he trains so hard," Sydney coach John Longmire said.

"He's got a crack in his hand, so it's three weeks or four weeks, I guess. [But] I'm not sure what the official diagnosis is.

"What Isaac is, is a really positive person. So he'll get over the disappointment of tonight and get to work and get himself right."

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Heeney managed only six games in 2020 until a serious ankle injury ended his season. 

There was concern early in the pre-season that the injury might force the 24-year-old to miss the start of 2021 too, or at least enter it underdone.

"He's worked so hard to come back from his ankle," Longmire said.

"He's been in great form for us this year, and a really important forward."

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