LUKE Parker and Tom Papley face major interruptions to their pre-season programs after undergoing surgery in recent days.
Parker's recovery from a PCL injury sustained in the preliminary final against Geelong hit a hurdle, and he had arthroscopic surgery on his left knee on Tuesday to assist his recovery.
Meanwhile, Papley faces two months off his legs after surgery to relieve the symptoms of compartment syndrome.
It looms as a huge blow to the second-year small forward's chances of repeating the success of his first season at the top level, when he booted 29 goals from 20 games as a rookie.
Parker, 24, didn't miss a game in 2016, averaging almost 27 possessions in his 26 matches, while also booting 25 goals, and bravely played in the Swans' Grand Final loss to the Western Bulldogs despite struggling with the injury.
Leading medical expert Dr Peter Larkins said Papley's injury was commonly found in runners and other participants of court-based sports.
Former No.1 draft pick Travis Johnstone had similar surgery after he was drafted to Melbourne in 1997.
"We say to patients that you're not going to be able to go back into running for a minimum of six weeks, maybe eight weeks," Larkins told AFL.com.au.
"The surgeons are really releasing the membrane around the muscle compartment, as sometimes the muscles expand within that tight little package with a heavy load of training.
"The muscle is so tight under the skin that it needs to be released, similar to how a sausage sometimes bursts when you're cooking a barbecue."
Sydney’s head of football Tom Harley said the club had hoped surgery wouldn't be needed for Parker, this year's Brownlow medal runner-up, but the injury hadn't responded as well as they'd hoped.
"Rest and recovery is the best typically (to heal a PCL injury) and Luke has been doing that since the Grand Final. He was starting to ramp up his training but the injury has regressed slightly," he said.
"It was decided a couple of days ago that an arthroscope is the best course of action and we fully expect Luke to recover well."
Papley's first-year haul up forward included nine goals in his four finals, giving the Swans' forward line a fresh look thanks to his tackling pressure and keen goal sense.
"Tom (Papley) developed compartment syndrome when he started to ramp up his off-season program and he required surgery last week to release the pressure in the compartments in both legs," Harley said.
"There's some wound healing initially that he will need to recover from and he will be off legs for the best part of eight weeks.
"It's disappointing but the success rate for this type of surgery is really high, so we're looking forward to Tom recovering well and hitting the ground running come the new year."
Larkins envisages Papley being able to complete 'seated' training within two weeks, if his body responds how it should and doesn't face any complications with infection over the next 10 days.
"It will be eight weeks that he'll be able to do some running out on the oval," Larkins said.
"Once the wound is healed up (after two weeks) he'll move into water-based activities, including work on the Alter G treadmill.
"I don't think his fitness will be too badly compromised through December or January, so it shouldn't affect his start to the season."
The pair join star forward Lance Franklin and ruckman Sam Naismith on limited programs before the Christmas break, with Franklin and Naismith expected to resume full training in the new year.