WEST Coast is sweating on scans to discover the damage to star forward Jack Darling after he hurt his right ankle against St Kilda, interrupting his career-best run of form. 

Darling suffered the injury in a marking contest late in the first quarter, landing on the boot of St Kilda defender Logan Austin.

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After staying down on the ground for several minutes he was eventually helped from the ground by trainers and taken to the rooms.

After riding a stationary bike, the star forward emerged in the second quarter on crutches, with his night ended.

"I don't know how Jack is. He wasn't good enough to come back on, so it was another ankle injury, so we'll find out with some scans and hope for the best," coach Adam Simpson said post-match. 

"I can't rule anything out on Jack. I'm worried, but I always worry. 

"I'm not a doctor. I'm not going to lie to you. I don't know how he is.

"I haven't spoken about how he's feeling.

"We'll find out tomorrow or the next day."

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Simpson said it was standard procedure for medical staff to try to get Darling back onto the field.

"I think they always try to do that. With ankles it's 'can you walk on it? Can we help it? What do we think it is?'" he said.

"When they don't know what it is they go 'let's just shut it down'. So that's what happened."

Darling has been a key contributor through the Eagles' nine-game winning run this season, kicking 28 goals to sit third on the Coleman Medal leaderboard.

The Eagles' forward unit has clicked around the contested-marking star, with Darling also averaging a career-high 7.8 marks, including 3.5 inside 50. His 31 contested grabs this season are an AFL high.

West Coast has a bye next week before taking on Sydney (SCG), Essendon (Optus Stadium) and Adelaide (Adelaide Oval).