Battle informed the Saints on Thursday he will use his free agency right to move to Hawthorn.
As an unrestricted free agent, Battle can join the Hawks without St Kilda having the right to match the offer.
Battle's decision came just two days after Barrass, who is contracted until 2027, told West Coast he wants to move to Hawthorn.
The Hawks will now have to satisfy West Coast with a suitable trade, with the Eagles expected to ask for two first-round picks as an initial bargaining position.
Battle, taken with pick No.39 in the 2016 national draft, played 123 games across eight seasons for the Saints.
He started his career as a forward before making a successful switch to defence, where he formed a strong combination with fellow key back Callum Wilkie.Â
"I came to this club while I was still in high school and couldn't have asked for a better place to grow, both as a footballer and a person," Battle said in a statement.
"I now have a young family of my own and in planning for our future I've come to the difficult decision to move on from my time at the Saints.
"The club has been fantastic throughout this entire process and I leave so grateful for the support they've shown both my family and I.
"I'd like to thank all my teammates, coaches and staff who have made my time at the Saints so special, as well as the Saints fans who embraced me from day one."
All the best, Batts �— St Kilda FC (@stkildafc) Josh Battle has today informed the club that he will pursue free agency opportunities with Hawthorn moving into next season.We thank Josh for his eight years of service and wish him and his young family all the best.Details → https://t.co/Qm7qrMvYLg pic.twitter.com/t8FILW3p8KAugust 29, 2024
The Saints could try to lure Melbourne's unrestricted free agent Adam Tomlinson as a replacement for Battle.
Richmond look set to be the club hardest hit during the trade period after Shai Bolton, Liam Baker and Daniel Rioli all requested trades.
The contracted Bolton is likely to join Fremantle, while out-of-contract Baker is yet to nominate West Coast or the Dockers as his destination of choice.
Rioli is keen to join Gold Coast to reunite with his former coach Damien Hardwick.
Collingwood defender John Noble also wants to join the Suns.
Melbourne premiership player Alex Neal-Bullen, who told the Demons two weeks ago he wants to head back to South Australia, is keen to link up with Adelaide.Â
He could be joined at the Crows by contracted Suns forward Jack Lukosius, who was dropped by Hardwick late in the season before winning back his place for the final game.
Collingwood have reportedly expressed interest in out-of-contract Suns midfielder Alex Davies.
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