But the Cats remain optimistic that key forward Tom Hawkins will play despite ongoing back issues that make him a day-to-day proposition.
Defender Josh Hunt is also a strong chance to replace the injured Corey Enright, who has a medial ligament injury. Hunt has played just 10 games in 2013.
The 20-year-old Caddy has played 17 games this season after joining the club from the Gold Coast, but struggled in the qualifying final on Saturday against Fremantle, gaining just nine disposals.
While he trained well on Wednesday, football operations manager Neil Balme said Caddy pulled up sore on Thursday morning and would miss the game.
Hawkins' fitness has been an ongoing concern and he was a late withdrawal from the first final. The club has been open about the issue but remain happy to wait until the last possible moment before ruling him in or out.
"He's not out of the woods completely but we're certainly optimistic," Balme said.
He said he did not think Hawkins would require surgery on his back post-season as it was more a matter of settling the back down, having a rest and then building strength around the area causing problems.
Enright will definitely miss after injuring his knee and Balme was not prepared to say whether the veteran defender would be available for a preliminary final.
"[It's] too early to be saying anything for sure there. We're really only worried about this game and if there is a reason for him to play on we hope he can get there. We're relatively optimistic, but he is no certainty," Balme said.
Balme said Trent West was in calculations to come into the team after the Cats struggled in the ruck last week against Aaron Sandilands.
However, he praised the efforts of Nathan Vardy and Mark Blicavs, particularly given they began the season third and fourth in line for the ruck duties behind West and Hamish McIntosh.
He said despite the Cats' keenness to debut Shane Kersten at some stage, it was unlikely he would play if Hawkins was in the team.
