North Melbourne on Monday ruled out Leigh Adams for the rest of the AFL season with the tough midfielder to undergo shoulder surgery.
Adams and 2011 joint club champion Daniel Wells (calf) were both injured during the first quarter of Sunday's round-20 clash with Essendon as the Kangaroos pulled off a courageous 24-point win, their fifth in a row which lifted them to sixth on the ladder.
Adams, who suffered an injury to his right shoulder in a controversial chicken-wing tackle from Carlton's Chris Judd in round 16, cut a forlorn figure as he struggled off the field during the first quarter of the Essendon clash at Etihad Stadium.
His left shoulder was dislocated and his arm was left hanging around his knee.
The Kangaroos are also monitoring the fitness of key defender Nathan Grima (hamstring tendinitis) ahead of Saturday night's Etihad Stadium clash with third-placed Collingwood.
North released a statement on Monday confirming 62-game veteran Adams would have season-ending surgery on his left shoulder.
"The club won't be in a position to make a call on the fitness of Daniel Wells and Nathan Grima until later in the week," the statement added.
Adams is averaging 19.1 disposals in 18 games in 2012. The 24-year-old has finished in the top five in North's past two best and fairest awards and coach Brad Scott says the 176cm midfielder's absence will be keenly felt.
"Internally he's extremely highly rated. We see him as a vital member of our team," Scott said on Monday.
"He's one of those heart-and-soul players. The players love having him in the team.
"You just know what you're going to get from him every week.
"He's been vital for the last three years, not just this year.
"He'll be a big loss," Scott told SEN Radio.
The Kangaroos will regain midfielder Jack Ziebell and small forward Lindsay Thomas from suspension this week.
Vice-captain Ziebell says he's determined to have an impact after serving a four-game ban and completing two weeks of high-altitude training in Utah.
Ziebell, who debuted in 2009, hasn't played in a winning side against Collingwood, who thrashed the Kangaroos by 117 points in round 16 last year.
Collingwood have won their past four games against North by an average margin of 80.5 points.
"Coming off a few wins and knowing we're in good form is a good confidence-builder," Ziebell told reporters on Monday.
"We're in a good position to take them on."
Ziebell says he won't modify his aggressive playing style despite his latest suspension.
"I've been brought up to attack the ball ferociously," he said.
"So if I was to be put in that position again, not much would change."