The ruckman/forward experienced some tightness in his back after Geelong's final training session before the team flew to Brisbane.
Vardy, who has battled hip problems in the past, has played two matches for the Cats in 2013, taking his career tally to 13.
Simpson has been in good VFL form, averaging 36 hitouts a game in five games, after overcoming back surgery at the start of 2013.
