GEELONG defender Jackson Thurlow will miss the 2016 season after scans on Monday confirmed a ruptured anterior cruciate ligament.
The 21-year-old was stretchered from the field after his right knee buckled underneath him in a marking contest with former teammate Mitch Brown in Saturday's NAB Challenge hit-out in Shepparton.
"Confirmation that Jackson has torn his ACL is extremely disappointing for him and the club," Cats football manager Steve Hocking said.
"His development came along in leaps and bounds last year and he was definitely in the mix to become a permanent member of our back six this season after showing great promise throughout the pre-season.
"As a club we will ensure he is provided with all the support he needs to work through the process."
It is a devastating blow for the Cats who viewed Thurlow as a lock in their best 22 as the club's pre-eminent rebounding defender, alongside veteran Corey Enright.
He averaged 17.3 disposals per game last season and was third at Geelong for rebound 50s in 2015.
Thurlow's precise kicking skills, his aerial ability in one-on-one contests and zippiness off half-back will be difficult to replace.
The latest setback continues a frustrating run for the young Cat, after he missed the first two games last season due to a potentially serious kidney injury.
Thurlow copped a stray elbow at training and spent six days in hospital with a lacerated kidney before Christmas.
The Cats have a few options to replace the emerging defender, with rookie Tom Ruggles soaring into contention after a strong performance against the Bombers.
Jed Bews, who faces a fitness test on his sore shoulder ahead of Geelong's final pre-season match against Fremantle on Saturday, will also be in contention based on his lock-down capabilities.
Luckless defender Josh Cowan may also be considered and has played in the Cats' two NAB Challenge matches so far.
Thurlow was drafted at pick 16 in the 2012 AFL draft and has played 29 games for the Cats over his three seasons with the club.