North Melbourne defender Declan Mountford faces a delayed start to the season after injuring his shoulder.
The Roos have confirmed that Mountford injured his AC joint at training on Monday and will miss up to a month of training following surgery.
Mountford, 21, re-signed with the Kangaroos on a one-year deal last October after making his debut in 2017 and playing 12 senior games.
Meanwhile forward Mason Wood (fractured thumb) will be held out of full contact drills for up to three weeks.
However, skipper Jack Ziebell has fully recovered from the injuries that plagued him last year and is ready to play in the season-opener.
Ziebell was on a modified training program until early January after undergoing toe surgery and having also endured rib and collarbone injuries in 2017.
"He did a lot of preparation without doing a lot of full training prior to Christmas, but he's come back from the break in great shape ... he's ready to play any time," coach Brad Scott said on Wednesday.
"We're just working with him now to get him in absolutely perfect shape for round one.
"How we structure that we're not quite sure yet. He won't play AFLX but we expect him to be absolutely right for (the first pre-season competition game)."
In other good news for North, veteran goalkicker Jarrad Waite has enjoyed an excellent preparation ahead of his 16th AFL season.
Waite, who has just turned 35, was restricted to 10 games last year by shoulder and calf injuries.
But he will play in the AFLX tournament and Scott is bullish about his prospects this year.
"It is a strange thing to say about someone of his age, but he feels - and I agree with him - that his best footy is ahead of him, and he's obviously played some high level footy in the past," Scott said.
"We'll probably manage his pre-season games to a certain extent, but I think the AFLX game will suit him.
"He wants to get out there and play, and while he is really enthusiastic, we want to get our best players out there and having a crack at this concept."