ST KILDA captain Jarryn Geary will undergo surgery on Friday afternoon to repair a broken leg.
The 32-year-old was assisted off the field after landing awkwardly in a marking contest at training at Sandringham on Friday morning, with scans later revealing he had suffered a fractured fibula lower down on his left leg.
However, the Saints are hopeful Geary could resume running within six weeks.
"Unfortunately, X-rays confirmed a fracture, which means Jarryn will be sidelined for a number of weeks," Saints chief operating officer Simon Lethlean said.
"Knowing Jarryn, he will do everything he can to be back as quickly as possible to contribute to the team in early 2021.
"Given his previous injuries, it's obviously frustrating to encounter another setback.
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"But the positive for Jarryn is that he's been here before, and we have full faith he'll attack his rehab with the same professionalism and intensity we know he brings.
"We had a number of guys step up last year and take their opportunities, and this year will be no different."
The defender, who also played forward for spurts of last season, enters 2021 on a one-year deal after holding the position as captain over the past four years.
The Saints currently have three positions open to be filled in the Pre-Season Supplemental Selection Period (SSP) after passing on three selections in last year's Rookie Draft.
Ex-Roo Mason Wood has been training in hope of winning one of the spots and any move for Geary to the long-term injury list could open another berth.
Any position left open can be utilised in the Mid-Season Rookie Draft, currently scheduled for June.