SYDNEY has been dealt a big blow with emerging half-back Callum Mills to miss the rest of the season after breaking his foot walking from a café.

The 2016 NAB AFL Rising Star winner suffered the injury on Thursday following training at the SCG.

He was with teammates and was throwing a gridiron ball on the way back to the club after being in the Moore Park precinct when Mills tripped and fell.

Swans coach John Longmire described the incident as innocuous.

"He was walking back from the café at Sydney Football Stadium here this afternoon after training, tripped and fell and broke his foot," Longmire said. 

"It's a really unfortunate accident and unfortunately he has an operation on Monday and he will be out for the rest of the year.

"It's a bad break and something out of the blue and something really disappointing for him and us."

The Swans have brought in Harry Marsh to fill the role of Mills across the backline as one of two changes, with Gary Rohan sitting out the trip to the Gabba to face Brisbane. Ryley Stoddart has been brought in for his debut.

Mills' obscure injury circumstances follows other bad luck the Swans have had outside the SCG.

Last year important defender Dane Rampe suffered a broken arm in a freak accident when he tripped on a chain and fell while doing recovery outside the ground.

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