Charlie Dixon booted four goals as Port Adelaide gave their top-four hopes a massive boost by outlasting GWS to snare an impressive 27-point win at Marvel Stadium.
Both sides had a disrupted build-up to Sunday night's hastily rescheduled contest, with the Giants making a mad dash to Melbourne on Saturday from their temporary base in Queensland after the snap lockdown was announced.
The Power surged out to a 27-point lead in the second term before riding out a wave of GWS momentum and pulling clear again to prevail, 15.10 (100) to 11.7 (73).
Port dominated the inside-50 count (65-46), laid more tackles than the Giants (62-47) and won contested possession (149-141) in a hard-fought contest.
"It was a really strong performance by the boys, I liked the way we were challenged again and GWS are a really good side with plenty to play for," Power coach Ken Hinkley said.
"We've been asked a few times in the last couple of weeks to respond and we've been able to do that.
"We had a pretty dominant game when it comes to the numbers and the stats and I know there's significant improvement still in us."
GWS lost key defender Phil Davis to concussion and saw Jacob Hopper taken from the field on a medi-cab with the same issue after he was accidentally kicked in the head while attempting a smother.
Daniel Lloyd and Sam Reid both played on despite ankle injuries.
Those woes compounded a difficult night for the Giants, who missed the chance to climb back into the top-eight.
"We got cut up in terms of scores from stoppage and their fleet-footed players got some real traction from stoppage and really hurt us, that was the difference in the end," GWS coach Leon Cameron said.
"The effort was there to the end and I expect nothing different.
"I thought we had one hell of a crack at it but in the end they're fourth (on the ladder) for a reason and we're sort of hovering around 8th, 9th and 10th for a reason."
Power midfielder Ollie Wines was a thorn in the Giants' side, tallying 28 disposals and four clearances in another strong display alongside on-ball partner Travis Boak (24 and seven).
Tall forwards Dixon, Peter Ladhams (three goals) and Mitch Georgiades (two) all posed problems for the Giants' defence.
Port Adelaide dominated early and while GWS hit the front during the third term, goals to Dixon and Orazio Fantasia gave the Power breathing space early in the final quarter.
Lloyd kicked three goals for GWS and Toby Greene booted 2.4 on return after two games out of the side in isolation, while Josh Kelly (32 disposals) and Hopper (28) battled hard in the midfield.
Australian Associated Press