St Kilda list boss Graeme 'Gubby' Allan says Pick 7 and Sam Flanders will be a direct swap.
The Saints won the race for the Gold Coast midfielder's services, as Essendon, Melbourne, and briefly Carlton made a play.
The Moorabbin club has been on the front foot in the 2025 player movement space, successfully luring Carlton free agents Tom De Koning and Jack Silvagni.
Leek Aleer and Liam Ryan are also expected to make their way to St Kilda via a trade.
However, Allan was "surprised" that Flanders nominated the Saints as his preferred destination amid a host of lucrative offers from Victorian rivals.
"I was surprised," Allan said on day one of the 2025 trade period.
"Yeah, we thought he might've gone to another club. He had some good offers."
The re-signing of Nasiah Wanganeen-Milera is seen as a major factor in the club's uptick in attracting rival players.
"I think with Naz signing, it really was important for us. With that, Naz signing, I'm not sure talking to you guys.
"I think (it's a game-changer)."
Potentially departing the club are contracted duo Jack Steele and Rowan Marshall, with the latter having requested a trade to Geelong.
Marshall has expressed his desire to play for the Cats next season, a club that reportedly spoke with Marshall in early September about a potential move down the highway amid the talent squeeze at Moorabbin.
The Cats' ruck stocks have long been considered to require a boost, with 34-year-old Rhys Stanley evidently no longer the best option for them moving forward following an underwhelming grand final performance.
Steele, locked away for 2026, has also been told he can explore his options.
Allan says that the Saints haven't spoken to any clubs regarding their skipper's future.
"We'll do what's best for the St Kilda footy club," he said.
