The Sydney Swans have made two changes to their side to face Brisbane Lions at the Gabba on Saturday headlined by the debut of 18-year-old Ryley Stoddart.

Stoddart and defender Harry Marsh comes into the side to replace Callum Mills (broken foot) and Gary Rohan (omitted).

Mills is expected to miss the remainder of the season after suffering an broken foot in an accident following training at the SCG on Thursday afternoon.

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

Longmire said he was confident Marsh would be able to step up in the absene of Mills. 

"He’s been very good," he said.

"He’s played some good senior football for us this year and his reserves form has been outstanding."

"He’ll be expected to play that role that Callum played."

Longmire said he was pleased the club was able to blood a third debutant this season.

"It’s one of the great joys in footy as a coach to be able to tell a player that they’re playing their first game," he said.

"Ryley was great over the pre-season and played some senior football.

"He’s quick, he’s got some really good run, he can play a variety of roles and he’s a good kick and decision-maker.

"He has the trust of the senior players and we look forward to seeing how he goes."

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