North Melbourne will be forced to make at least three changes ahead of Sunday's twilight clash with the Saints, with midfielder Tom Powell (ankle) and talls Charlie Comben (ankle) and Callum Coleman-Jones (concussion) ruled out.

With Coleman-Jones out short-term and Comben expected to miss the next 10 weeks, key defender Griffin Logue may be called upon to fill the second tall-forward void.

The loss of Coleman-Jones in the third term against the Demons prompted Alastair Clarkson to shift Logue into the forward line to partner Nick Larkey, a position the backman hasn't played since he booted two goals for Fremantle in its 2022 semi-final.

His possible switch forward could see Aiden Bonar or Kallan Dawson brought in to assist Aidan Corr and Ben McKay in combating St Kilda's tall targets in Mitch Owens, Tim Membrey and Zaine Cordy.

Dawson and Bonar could also be included in the event Jack Ziebell (foot) fails to prove his fitness.

The veteran limped down the race and into the rooms prior to the quarter-time siren at the MCG, and will have his functionality assessed during Thursday's main training session.

Named an AFL emergency for the first time last weekend, Blake Drury could come in for Ziebell, but after a spell at half-back the 19-year-old has found form in the reserves as a half-forward, with three goals from the last two games.

Lachie Young, Miller Bergman and Flynn Perez also shape as potential half-back inclusions.

Like Ziebell, Luke Davies-Uniacke (heel) and George Wardlaw (knee) will undergo fitness tests on Thursday. The former has now missed two games this season, taken out of the team after selection on each occasion.

In hot form over the early rounds, he is the likely replacement for Powell if given the green light.

The onball contingent of Will Phillips, Hugh Greenwood and Charlie Lazzaro impressed in the reserves' 15 v 15 hitout last Saturday morning against the Saints, with all members pushing forward strong cases for selection.