St Kilda leaders Nick Riewoldt and Leigh Montagna face fitness tests on Wednesday which will determine whether the pair head to New Zealand for the Anzac Day match against Carlton.
The Saints depart for Wellington early on Thursday morning, meaning both will need to prove their readiness by midweek.
Riewoldt was a late omission from the team thrashed last Friday night by Collingwood, with the captain and six-time best-and-fairest winner pulled at the last minute with calf tightness felt during the warm-up. Club doctor Tim Barbour suggested Riewoldt was on the mend, but remained no certainty to play.
"That was in a different area to what he had during the week. He had a slight strain on his MRI and he's settling well, but he will be tested midweek," Barbour told the Saints website.
"A decision will be made on Wednesday."
Midfielder Montagna had minor surgery on his knee to repair a meniscus issue late in the pre-season, and has missed the past two games after playing in round one.
Pint-sized St Kilda forward Jack Lonie will be available, after recovering well from the jarred knee which forced his substitution against the Magpies. Unlucky defender Sam Gilbert will return this weekend to play his first game since August, set to take the field after overcoming a longstanding foot issue.
Meanwhile North Melbourne are also sweating on the fitness of star midfielders Jack Ziebell and Daniel Wells, along with defender Jamie MacMillan.
Ziebell spent two nights in hospital following a brutal collision during Saturday night's game against Port Adelaide which caused the midfielder to sustain a bruised lung, while Wells and Macmillan have been nursing Achilles injuries which have led to one and two weeks out respectively.
The club's football director Geoff Walsh was hopeful of all three lining up for the Roos' clash with Geelong at Simonds Stadium on Sunday.
"With an eight-day break, we've been able to give those three guys every chance to put their hand up to play on Sunday," Walsh told the North Melbourne website.
