“We have been working closely with Paddy, his loved ones, his doctors and his management for some time,” St Kilda's General Manager of Football Simon Lethlean told the club's website.
“We feel it is important for Paddy to focus solely on his physical and mental wellbeing without the pressure of returning to senior football in the 2020 season.
“This decision gives him the best opportunity to ultimately resume his career, with the club open to re-listing Paddy should he be healthy and physically ready to attack a pre-season at the end of 2020, and play senior football in 2021.
“As Paddy explained during the year, this injury has had a significant impact on his life, and general health and wellbeing.
“It has been a difficult time for him, his family, the people close to him, and for his teammates, coaches and support staff who know how hard he has worked to put himself in a position to succeed at the elite level.
“He is a really popular member of our playing group, and we saw during the 2019 pre-season what sort of footballer he was becoming.
“We also wish to recognise that Paddy has not only considered what is best for himself, but also what is best for the club in coming to this tough decision. This is commendable and we thank him for that.
“The club has also committed to assisting him with activities and pursuits of interest to him both within football and outside of football as part of his focus over the next 12 months."
Dal Santo lamented the fact McCartin's immense potential seems likely to go unfulfilled.