In a nail-biting finish to Saturday night's match, West Coast came from 22 points behind late in the third quarter to close the margin to four points with three minutes remaining.
The ball lived in West Coast's forward line for most of the last quarter, and the Eagles had their chances to snatch the lead.
But Port were able to finally clear the ball from their defence in the final two minutes of the game, with Mitch Georgiades kicking a point after the final siren to make it a six-point win, 11.11 (77) to 10.11 (71), in front of 47,479 fans.
The result improved Port's record to 4-8, while the Eagles slipped to 4-9.
But the biggest news of the match was the injury to Ginbey.
Ginbey had kept Georgiades goalless in the first half, but tore his quad while chasing the star Power forward 10 minutes into the third quarter.
The injury came just days after Ginbey re-signed with West Coast until the end of 2030, and just a week after Eagles coach Andrew McQualter said the 21-year-old was in All-Australian form.
"It didn't look good, certainly made me a little bit sad, as I imagine it did for all of our Eagles supporters," McQualter said of the injury.
"But we don't know. We'll go away, we'll do all the tests required and see what happens."
Port were also dealt a blow, with Josh Lai concussed after running into teammate Esava Ratugolea.
Port midfielder Zak Butters racked up 27 disposals and seven clearances despite having to deal with tagger Brady Hough, while defender Esava Ratugolea tallied seven intercept marks in a masterful display.
Jason Horne-Francis kicked three goals for Port, while Jake Waterman kicked three for West Coast and defender-turned-forward Tom Cole kicked two.
Eagles premiership defender Cole could have levelled the scores with four minutes remaining, but his 40m set shot missed.
Butters endured a forgettable start to the match, the star Power midfielder copping an accidental boot to the head from Liam Baker, before watching on hopelessly from the bench as his opponent Hough kicked the opener.
Port should have led by more than six points at quarter-time, but their wayward return of 3.6 ensured West Coast stayed within striking distance.
Harley Reid was left feeling miffed at the quarter-time siren after his offer to help Butters get up from the ground was rejected by the stand-in Port skipper.
The skill level on display from both sides in the second quarter was simply horrendous, with the only saving grace for the game at halftime being the fact it was still close.
Waterman was left fuming after dropping a mark in the goal square late in the second quarter, and he shook his head in dismay moments later when his shanked set shot still managed to sneak through.
Port led by 11 points at halftime, and extended the margin to 22 points late in the third quarter before a Cole goal on the run gave West Coast hope entering the final change.
The Eagles dominated the final term, but their return of 2.6 proved costly.
"It probably got a little bit too tight there in the end," Port coach Josh Carr said.
"But an away game in front of a big crowd under a lot of pressure - it was nice to just get the win in the end."
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