West Coast's worst fears have been confirmed, with scans showing star ruckman Nic Naitanui has torn the anterior cruciate ligament in his right knee.
Naitanui suffered the injury in innocuous fashion during the second quarter of Sunday's AFL win over Collingwood at the MCG.
The 2012 All-Australian underwent scans on Monday morning, with Eagles coach Adam Simpson later confirming the ACL rupture.
Naitanui missed all of last year after tearing the ACL in his left knee in 2016.
If the 28-year-old needs a similar recovery time for his latest injury, it's unlikely he'll play at all next year.
Players normally need around 10-12 months recovery time from traditional knee reconstructions.
But given Naitanui's size and explosive nature, West Coast took a conservative approach last time, giving the big man closer to 19 months.
The injury is a bitter blow to second-placed West Coast, who are well positioned to mount a premiership assault.
Scott Lycett will now be handed the responsibility of leading West Coast's ruck, with former Cat Nathan Vardy a chance to earn a recall as support.
Naitanui exceeded expectations in his comeback this year, and he showed he had lost none of his amazing leap with a mark-of-the-year contender against GWS in round 16.
But whether he can return with a bang from a second serious knee injury remains to be seen.
"He's huge for us - spiritual leader for us out there," Eagles midfielder Luke Shuey said of Naitanui's influence.
"He can get 21 guys going just off one act, and that's a pretty special trait to have.
"We'd be shattered for him (if the ACL is confirmed). But in terms of our season, nothing changes.
"Scotty Lycett did a terrific job yesterday in the second half, and had to carry a huge workload against one of the best ruckmen in the competition.
"Scotty's come along in leaps and bounds this year. If things don't work out for Nic, then I'm really excited to see what Scotty can do."
Shuey said all the players felt for Naitanui, who also dealt with the passing of his mother in 2015.
"It's been a tough trot for him," Shuey said.
"You don't want to compare things that happen in your personal life to your footy life, but they certainly compound each other.
West Coast (12-4) will be aiming to continue their good form when they take on the Bulldogs at Optus Stadium on Sunday.
