West Coast coach John Worsfold says a stunning 18-point upset of Port Adelaide has delivered something as valuable as AFL premiership points - belief.

Last year's wooden spooners completed confidence-boosting consecutive wins to start their new season with a 16.20 (116) to 15.8 (96) triumph at AAMI Stadium on Saturday.

The Eagles were inspired by evergreen Andrew Embley's sheer brilliance - he trounced noted Port tagger Kane Cornes, kicking four goals, gathering 32 possessions and taking 11 marks.

West Coast led Port for the entirety of the contest before 23,214 spectators, with only inaccurate goal kicking threatening their control as Port twice crept within five points in a tense last term.

But the Eagles held sway with Embley fittingly kicking the last goal of the match to seal victory.

Port's second successive loss came at a high cost, with captain and key onballer Dom Cassisi to have scans on an injured knee.

Cassisi was substituted at halftime with a suspected medial ligament strain which coach Matthew Primus said would likely need surgery.

Cassisi's absence was sorely felt as the Power relied too heavily on the gifts of goalsneak Robbie Gray, who kicked four goals in a standout performance.

Worsfold's Eagles return to Perth to host Sydney next week with burgeoning belief after winning without injured sharpshooter Mark Le Cras.

"They have certainly still got a lot to learn," Worsfold said of his players.

"(But there is) a bit more belief about themselves, that they're going to match it and are going out to win games.

"Really today with Le Cras out, there were no second thoughts that we weren't a lesser chance to win the game ... just that belief within the group is a lot stronger."

Worsfold was heartened by the comeback of midfielder Daniel Kerr, influential in collecting 25 possessions in his first game since tearing a hamstring off the bone in round four last year.

Forward Josh Kennedy commanded the attack and finished with three goals, defender Shannon Hurn was creative and emerging 20-year-old Luke Shuey (27 disposals) also booted three majors.

Shuey's midfield colleague Matt Priddis (29 touches) shone while Dean Cox was masterly in the rucks with 21 disposals and 34 hit-outs to easily eclipse Port's Dean Brogan.

"We really got blown away early in the game," Primus said.

"The first half was disappointing ... they had a lot better work rate than us and we were struggling for periods there with Dom coming off."

Defender Paul Stewart (knee) is also in doubt for Port's away trip to Geelong next Sunday.

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