Fremantle have come from behind at the final change, kicking the opening six goals of the fourth quarter to defeat GWS in their AFL clash in Canberra.
Leon Cameron had labelled the Dockers one of the competition's form teams and the Giants coach was proven correct, with his men upset 16.10 (106) to 11.16 (82) on Saturday.
GWS were unbackable favourites heading into the contest and could have gone top with a win but it was the Dockers who instead climbed into second spot.
Returning skipper Nat Fyfe finished with 31 disposals for Fremantle, while Brandon Matera kicked four goals in front of 11,277 fans at Manuka Oval.
The Dockers wasted chances with some point-blank misses and poor set shots early but delivered when it mattered.
Coach Ross Lyon highlighted the performance of ruckman Rory Lobb in winning six of eight final-term centre bounces in his first game against his former club.
"It was a really tough battle all day, really see-sawing, both teams giving great effort and we got on top in the last quarter, Rory Lobb was significant at the centre bounce," he said.
"It's always won and lost in the midfield and in the end I thought our midfield got on top. We sort of made our own luck with persisting and persevering.
"All day we fought hard and in the end we got an edge ad took our opportunities."
GWS were left to rue missed opportunities as wayward kicking and a lacklustre fourth term cost them in the capital, where they had won nine in a row.
"They just worked harder. Fremantle deserved to win and were probably the better side for 80 per cent of the game," Cameron said.
"When the whips were cracking in the final quarter they worked really hard. Around the hunt they beat us up, so that's disappointing.
"Collectively across every line we were disappointing. They probably had over 15 or 16 players as winners and we probably had four or five and you just can't win games of footy that way."
Giants star midfielder Stephen Coniglio topped the charts with 37 disposals, while Jeremy Cameron booted four goals in the absence of injured star Callan Ward.
Dockers defender Taylin Duman could find himself in trouble with the match review panel after shoving Lachie Whitfield in the face but will likely just cop a fine.
GWS veteran Matt de Boer was tipped to shadow Fyfe but the in-form tagger went to Bradley Hill and also spent time on Andrew Brayshaw.
Giants co-captain and key defender Phil Davis went off in the final term with an ankle injury.
Australian Associated Press