In: David Armitage, Jackson Ferguson, Nathan Wright, Josh Saunders
Out: Lenny Hayes

Milestone: Leigh Montagna - 200 games

St Kilda has named an extended seven-man interchange bench ahead of its match against North Melbourne on Sunday.

Veteran midfielder Lenny Hayes has been left out due to a calf injury, while Leigh Montagna will play his 200th game this weekend.

Potential debutant Jackson Ferguson has been named in the squad of 25 to be trimmed on Friday after being elevated from the rookie list this week for Daniel Markworth.

The strong-bodied 20-year-old is a key defender and came to the Saints via the AFL Rookie Draft in 2011, pick 72 and has been in excellent form in the VFL this year. If he is selected in the final 22, he will be the Saints sixth debutant this season.

Also in line to return is classy midfielder David Armitage after he was a late withdrawal last Saturday. The left-footer collected 25 possessions and booted two goals the last time St Kilda met North Melbourne in round 14, 2012.

Joining Ferguson and Armitage on the extended bench is Josh Saunders and Nathan Wright, the latter having recovered from a broken jaw sustained against Carlton in round seven.

Hayes is expected to miss 2-3 weeks, while Markworth has been placed on the long-term injury list after tearing his ACL in December.

You can follow Tom Morris on Twitter: @tommorris32