West Coast's pre-season opener against Essendon was soured on Thursday night by news that premiership forward Daniel Venables will sit out the 2020 season as he works his way back from a serious head knock.

Coach Adam Simpson confirmed that the 21-year-old had made the decision to step away after deep consideration as he continues to deal with lingering symptoms from a head knock suffered in round nine last season.

Venables will be placed on the long-term injury list and the Eagles will consider adding another player during either the Pre-Season Supplementary Selection Period or the AFL Mid-Season Draft.

"We've worked very hard with Dan to try and get him best prep and see where he's at physically, (but) it just hasn't pulled up well enough and he's going to take the rest of the year off," coach Adam Simpson said on Thursday night.

"It's really disappointing for him and obviously his family, but it's the right thing to do. 

"He's going OK, he's going well, but it gets to a certain point where he can't go to that next level and I think the best thing for him and his health would be to pull it back.

"They've made that decision with the docs and he won't play for the rest of this year and hopefully we see him back next year."

The Eagles said they would continue to monitor and support Venables, who has trained on a modified program this pre-season and experienced varying levels of discomfort after sessions.

The Eagles launched their Marsh Community Series campaign against Essendon on Thursday night, falling eight points short amid thunder and lightning at Mineral Resources Park.

Simpson said he walked away with a glass half full assessment of the performance, with veteran forward Josh Kennedy (six goals), new midfielder Tim Kelly (27 possessions and six clearances) and ruckman Nic Naitanui (28 hitouts on limited game time) ticking important boxes.

"We got jumped really early in the contest and work rate so that was disappointing, but we worked our way back into it," Simpson said.

"It was a bit of a grind in the end, the whole day, and they looked just a little bit cleaner at stages.

"But we take some positives from the day, some individuals, we came away injury-free which is important.

"We’ve got some work to do as well so probably around about where we thought we’d be at."

Kennedy's dominant performance delivered proof the champion forward is enjoying a strong summer on the training track, while Naitanui shone at stoppages after a full pre-season.

Simpson said both were prepared for the year ahead, having missed three of the past four pre-seasons.

"That doesn't mean you're going to have a great season, it doesn't mean you're going to be injury free. But it just builds a bit of resilience with your body," the coach said.

On Kelly, who worked into the game after a scratchy first half, Simpson said the star recruit had "a couple of fumbles like everyone else".

"We weren’t playing very well either," the coach said.

"He’s just one of our midfield group that probably lowered their colours for the early part of the game and worked their way into it."