Port Adelaide coach Mark Williams acknowledged his side's astonishing come-from-behind win over Fremantle on Saturday was a massive achievement, but only allowed himself five minutes to enjoy it before turning his attention to the Kangaroos.

Trailing Fremantle by 34 points eight minutes into the third quarter at Subiaco Oval, Williams' hungry brigade slammed home seven unanswered goals in 15 minutes to eventually win 19.7 (121) to 16.9 (105) and put an immediate dent in the Dockers' premiership aspirations.

Inspired by Dean Brogan's tireless tap work, and a succession of long-range goals from Damon White and new boy David Rodan, Port were able to avenge their last AFL outing - a 79-point hammering against the Dockers in round 22 last year.

Williams said having lost forward Daniel Motlop early to an ankle injury, the win was up there with his best in charge of the Power.

"It is right up there. It was a great effort from us to come back from where we were, I thought our fitness was outstanding ... we had to guts it out," Williams said.

"It is huge, but it is only one game - we get realistic with it.

"There is a lot of us who have been around for a while and we will enjoy the five minutes, suck it in and suck in the atmosphere.

"But right now the players are onto next week, and as much as you want to write us up, we know we are playing against a side (the Kangaroos) that beats us every time we play."