The Power trailed at every change and by 20 points midway through the third quarter before holding Melbourne goalless in the final term to bravely prevail 11.9 (75) to 9.11 (65) in front of a crowd of 40,751 at Adelaide Oval.

Recently re-signed midfielder Ollie Wines (29 possessions) led the way while Sam Powell-Pepper's 17 tackles was a new club record and two shy of the all-time AFL benchmark.

"I thought our pressure was through the roof," Port coach Ken Hinkley said.

"Our backline defended amazingly well under a fair bit of pressure.

"We found a way to keep in the game which was a credit to the boys."

Jack Viney (30 disposals, 14 clearances) and Max Gawn (53 hitouts) paced the visitors who looked on track all night before fading late.

Neville Jetta completely blanketed Robbie Gray early as Melbourne had the better of a 21-minute goalless stalemate before breaking the shackles with three goals in as many minutes.

Brad Ebert belatedly slotted Port's first major after the quarter-time siren and followed up with another early in the second.

Chad Wingard then converted from the pocket after contentiously being awarded a mark as the Power suddenly levelled the scores.

Despite the visitors' overwhelming dominance in inside 50s (39-17) and clearances (28-15), they led by only two points at half-time.

Melbourne again drew 20 points clear early in the third but the Power continued to chip away.

Robbie Gray emerged from Jetta's clutches with two third-quarter majors and Justin Westhoff marked strongly and goaled as Port reduced the gap to eight points at the final change before finishing with a rush.

Lindsay Thomas goaled after inexplicably being left alone to pouch an uncontested mark in attack before Sam Gray converted a free after being taken high by Jetta to give the Power their first lead since the opening minutes, as the Demons went ice-cold.

Westhoff bombed from range after Oscar McDonald conceded a 50m penalty before Angus Brayshaw was denied a mark well inside the Demons' 50 as Port slammed six of the last seven goals to storm home.

"We play a game of small margins and that game could have gone either way," Melbourne coach Simon Goodwin said.

"Our efficiency inside 50 wasn't at our best which is an area where we've been relatively strong most of the year.

"To Port's credit they continued to get better as the game went on."

Australian Associated Press