In control of the game up until half time, the Power failed to kick a goal in the third term against the Western Bulldogs at TIO Stadium.
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In contrast, the Bulldogs booted five consecutive majors to turn a nine-point deficit at the half into a 19-point advantage at the final change.
It made it difficult for the Power to turn around, but try it did.
A late series of goals saw the Power claw its way to within ten points with under four minutes remaining.
A mark to Angus Monfries in front of goals saw him quickly go back and take a set shot, but his subsequent miss left the deficit at nine points rather than four.
That margin would remain until the final siren.
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The result was made all the more disappointing given the Power's dominance of the first half.
Most key stats, particularly entries inside 50, showed Port had the Bulldogs covered, but several missed set shots left the Dogs in the game throughout the night.
Senior coach Ken Hinkley didn't pull any punches after the game, describing it has his "most disappointing" loss at the helm of the club.
Things were made worse when Jarrad Redden left the ground with a potentially season-ending shoulder injury midway through the final term.
Port Adelaide has a bye next weekend before returning for games against GWS, Sydney, Hawthorn, Collingwood and Essendon.
WESTERN BULLDOGS 2.0 4.0 9.4 10.7 (67)
PORT ADELAIDE 3.3 5.5 5.9 8.10 (58)
GOALS
Western Bulldogs: Giansiracusa 2, Jones, Williams, Griffen, Minson, Addison, Murphy, Dahlhaus, Johannisen
Port Adelaide: Wingard 2, Butcher, Hitchcock, Ebert, Boak, Westhoff, Logan
BEST
Western Bulldogs: Griffen, Liberatore, Morris, Murphy, Minson, Goodes
Port Adelaide: Wingard, Ebert, Cornes, Hombsch, O'Shea, Westhoff
INJURIES
Western Bulldogs: Tom Williams (right shoulder), Koby Stevens (right leg)
Port Adelaide: Redden (right shoulder)
SUBSTITUTES
Western Bulldogs: Daniel Giansiracusa replaced Tom Williams in the second quarter
Port Adelaide: Kane Mitchell replaced John Butcher in the third quarter
Reports: Nil
Umpires: Hosking, Kamolins, Jeffery
Official crowd: 7850 at TIO Stadium, Darwin
