THE FULL extent of West Coast's Derby injury carnage has been laid bare, with star trio Jeremy McGovern, Liam Ryan and Jamie Cripps all requiring surgery.

Cripps underwent surgery on his broken left ankle on Tuesday, while scans reveal that both McGovern (hamstring) and Ryan (hamstring) are likely to need surgery as well.

It was no surprise that McGovern needs surgery given how high up he tore his hamstring and the abrupt nature that he pulled up.

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But Ryan's setback comes as a huge shock because he was able to return to the field.

Ryan was injured after he crashed head-first to the turf after flying high for a mark.

He could barely walk after the incident, but bravely returned to the field in the final quarter of the 41-point loss to Fremantle.

It was initially feared he had injured his back or his knee, but scans have since shown a torn hamstring.

Cripps could miss the rest of the season with his broken ankle, while McGovern and Ryan are set to spend months on the sidelines.

The news was better for skipper Luke Shuey, who is only expected to miss two to three weeks with his own hamstring injury.

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But no timeline has been set for the return of Campbell Chesser, who injured his knee in the Derby.

Defender Alex Witherden will miss Sunday's clash with Melbourne because of concussion while Harry Edwards, who was in line to replace McGovern, is listed as a test after injuring his ankle at training.

Ruckman Nic Naitanui (Achilles) won't return until the middle of the season, but veteran Elliot Yeo (calf) could be back this week.

"We were proud of our players' spirit and determination in difficult circumstances against Fremantle, albeit disappointed not to get the result we were hoping for," West Coast's football manager Gavin Bell said.

"Unfortunately, from that match we've had some bad luck on the injury front, largely stemming from collision injuries, which we all accept are part of the game.

"After a heavy landing from a marking contest, Liam felt he was capable of returning to the field, and his desire to help the team with interchange rotations was admirable.

"Unlike last season, we have much better availability among our squad after 14 AFL-listed players represented the WAFL Eagles in their win over Subiaco on Saturday.

"We're really confident in those players stepping up to play roles as required and, while we'll do everything we possibly can to support our injured players' welfare, the team and coaches led by Adam Simpson are quickly refocusing on taking on Melbourne."