St Kilda expects mature-age rookie Rowan Marshall to provide a key target in the air in his debut against Sydney at the SCG on Saturday night.

The 21-year-old has been used predominantly in attack in the VFL this season, along with stints in the ruck and more recently at centre-half back.

With Tim Membrey serving the second week of his two-game suspension and Paddy McCartin still sidelined due to concussion, Saints Coach Alan Richardson is confident Marshall can execute his role in his first game.

“Rowan Marshall is a mature aged for a first-gamer; he’s 21 years of age,” Richardson said at a press conference at Melbourne airport on Friday.

“He’s a tall forward that can go into the ruck, we’ve played him in defence a little built at VFL level; he’s got some flexibility in his play.

“We’re certainly optimistic that he’s going to be able to give us a real contest in the air.”

Friday Microscope: Round 18 v Sydney

The match committee at Linen House Centre have made wholesale changes to the side that was comprehensively beaten by Essendon last Friday night, with four players dropped and one other forced change due to Sam Gilbert’s hand injury.

Contested ball winners Blake Acres and Luke Dunstan have been rewarded for their strong form with the Zebras, ruckman Billy Longer has overcome a hamstring injury, while rebounding defender Jimmy Webster returns after serving his suspension.

Richardson explained that St Kilda made such a large amount of changes due to a variety of reasons, including form, the Swans midfield makeup and the small dimensions of the Sydney Cricket Ground.

“(The changes were due to) a bit about the opposition we play and it’s a smaller ground; we’ve brought in some guys that win contest; our team is a much contested team; we still think we’ve got a really good balance in terms of inside and outside,” Richardson said.

It’s a slightly bigger forward line for the same reasons because of how small the ground is; it’s a wide ground but end to end it’s not a long ground. And some guys just didn’t quite get it done (against Essendon); they’ll go back to the VFL and work on their footy.”