St Kilda's forward line has been boosted by the return of youngster Paddy McCartin ahead of Saturday night's clash at Etihad Stadium.

Fresh from kicking five goals for the Saints' VFL affiliate Sandringham, 20-year-old McCartin hasn't played since early July after suffering his third bout of concussion for the season against Gold Coast in Round 15.

The merging forward, who's kicked 13 goals from his 15 career games, will complement a front half already boasting keys Nick Reiwoldt, Josh Bruce and former Swan Tim Membrey.

The latter two helped themselves to a share of the Saints' 27 marks inside 50s in last weekend's win against Carlton on top of kicking nine goals between them, with Membrey finishing with his fourth five-goal haul for the season.

McCartin replaces on-baller Luke Dunstan - out with a dislocated shoulder - as St Kilda's only change for the Round 21 clash.

With a mathematical chance at making finals, the Saints' cause will be made much easier with a win and if North Melbourne lose to Hawthorn.

That scenario will put them just four points out of the top eight with then two rounds remaining in the home and away season.

The home side will have to buck a recent trend to do so however, having lost seven of the past eight encounters against the Swans.

The clubs' last clash, in Round 22 under Etihad Stadium's roof, finished in a 97-point defeat.

Head to head: Sydney Swans v Carlton

Played: 212
Sydney: 132
St Kilda: 77
Draws: 3

Last time we met:

Round 22, 2016, Etihad Stadium
Sydney 20.15 (135) d St Kilda 4.14 (38)