WEST Coast will have to contend for the 2018 premiership without Nic Naitanui after confirming the star ruckman needs a second knee reconstruction.

The Eagles' worst fears were realised after scans on Monday revealed their spiritual leader ruptured the ACL in his 'good' right knee during the second quarter of a 35-point win over Collingwood at the MCG on Sunday. 

The 28-year-old's knee twisted slightly as he landed after contesting a boundary throw-in and he crumpled to the ground immediately.

"Unfortunately, he does (need a reconstruction). Really disappointing for Nic and the club," coach Adam Simpson told Channel Seven.

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"We can't dwell on it for too long. We've got a game coming up pretty quickly and Nic knows that, he's been through it.

"My heart goes out to him.

"Personally, it's a long road back. He spent a good 16 or 17 months getting back to fitness.

"He did make a difference for us for this part of the year but he'll go through the same process and he'll be back better than ever.

"In the meantime, we need to get on with the season.

"He's obviously disappointed but he's remaining upbeat. He understands where we're at as a club at the moment and what needs to happen.

"I'm sure in the coming days and weeks it will sink in, the work in front of him.

"But he's not scared of hard work and the journey will continue."

Naitanui was only 15 games into his comeback from an ACL tear in his left knee suffered against Hawthorn in round 22, 2016.

His injury is a major blow to the second-placed Eagles' premiership hopes, given Naitanui's significant impact around stoppages and on West Coast's midfield since his return.

The 201cm big man took 19 months to get back on the park from his first knee reconstruction, when his rehabilitation was complicated by bone damage.

Naitanui pushed to be part of last season's finals series but his hopes were dashed after the Eagles crashed out in a semi-final loss to Greater Western Sydney.

The ruck load will now fall to restricted free agent Scott Lycett, whose importance to West Coast's flag ambitions has increased significantly.

"We really needed him on the weekend, and really pleased that he played an important part to nullifying a really good ruckman in (Brodie) Grundy, it was probably almost break-even, which was great," Simpson said.

"The boys stood up in that game. It was an important game for the season and what we need to do at the MCG."

Nathan Vardy is also expected to come into the frame as a second ruckman after playing 22 matches last season in Naitanui and Lycett's (shoulder) absences.

The injury-plagued former Cat has made only one senior appearance in 2018 – in round 16 against the Giants - after running into adductor trouble in the first half of the campaign.