Dylan Roberton will sit out the 2019 AFL season due to an ongoing heart condition, although the St Kilda defender has not ruled out the possibility of resuming his career in 2020.
Roberton only played four matches last year before collapsing on-field during a game against Geelong.
The 27-year-old suffered another incident of heart irregularity - the cause of which remains unknown - during a recent pre-season game in Ballarat.
Roberton had previously undergone extensive testing from cardiologists and had a defibrillator installed before completing a full pre-season.
"It's extremely frustrating because I physically feel fine, and if you exclude those two incidents, I'm as healthy as I've ever been," Roberton said on Friday.
"Unfortunately, I need to listen to the professionals and take some more time.
"I still have a great desire to play at the highest level and want to make sure we look at every possibility.
"Given the club's ability to add a player to the list, I wanted to make the call while they still had time to do so."
St Kilda coach Alan Richardson praised the resilience of Roberton, who had enjoyed a career-best season in 2017, finishing second in the Saints' best-and-fairest award and earning an extended All-Australian squad berth.
"Robbo is an incredibly selfless player, and nothing speaks more to that than his want to continue to play on and contribute to our group. Unfortunately, that's not going to happen this year," Richardson said.
"To lose a player of his calibre is no doubt a blow, but as he said to his teammates when he spoke to them today, he has enormous faith in our guys to step up and fill the void.
"The club, our medical staff, coaches and the players will support him through this period and with whatever comes in the future.
"Whether that's working with the coaching staff again like he did last year, I'm sure Dylan will still play an important role for us in 2019."
The loss of Roberton continues a dreadful recent run of luck for the Saints, who were looking to bounce back this year after a dreadful 2018 campaign saw them finish third-last with just four wins.
Key defender Jake Carlisle will miss most of the year with a back injury, spearhead Paddy McCartin is under a cloud for round one after suffering yet another concussion and reigning club champion Jack Steven has taken time away from the club to deal with a mental health issue.
St Kilda play Gold Coast at Marvel Stadium on March 24 in round one.