Four goals from Hugh McCluggage helped Brisbane take care of business in their pursuit of a top-four berth, seeing off GWS in their first-ever trip to Canberra.
Lions coach Chris Fagan admitted the 15.9 (99) to 9.5 (59) win was crucial, seeing them entrench themselves inside the top four and move equal-top with Geelong, Melbourne and Fremantle, who are all yet to play in round 18.
Four first-half goals for Toby Greene kept the Giants within seven points at half-time, but they were blown away, conceding nine of the next 10 goals.
With a number of key players back in the lineup after being out with COVID and others still missing through injury, Fagan said he was very proud of the 40-point win.
"It's been a pretty unsettling couple of weeks at the club with COVID and injuries and a narrow loss last week," he told reporters.
"Our contest today was outstanding; winning contested ball, winning clearances ... but the thing that was most pleasing for me was we were able to keep the Giants to 35 inside 50s, and 14 of them were in the last quarter.
"That tells you that we put on a really tremendous defensive performance today, which is very pleasing because we weren't happy with that part of our game last week."
McCluggage was at his sparkling best with 30 disposals to go with his majors, but they got a huge boost from Rhys Mathieson in his first AFL appearance of the year, racking up 10 clearances among his 23 touches.
With Jarrod Berry, Dayne Zorko and Daniel Rich still out of the line-up, Fagan said Mathieson's brutality at the contest had given him the best kind of problems at the selection table.
"We thought Rhys would be a good inclusion this week, and I'm sitting here thinking maybe we should have thought that a little while ago, maybe picked him a little bit sooner," he said.
"Typical of Rhys, he gets his opportunity, puts his hand up and delivers for us and 10 clearances is a wonderful effort."
Outside of Greene's goals, 30 disposals for Harry Himmelberg and a gutsy defensive display from Sam Taylor, the Giants were soundly beaten, smashed by 25 extra clearances and 25 extra inside 50s.
"I was extremely disappointed with some of their efforts, especially to stop them scoring, to defend the ground, to stop the transition run from their midfielders ... we were exposed badly in that area," GWS coach Mark McVeigh told reporters.
"And then what heightens that is you go down and lose contested position by 17, which is a pretty alarming trend at the moment for our club."
Now 5-12 and firmly out of contention with five games to play, McVeigh admitted he was worried losses could start to pile up.
"There's five weeks to go, so it's a long time and what they do need to find is what they want for the rest of the year ... you can't just have a heavy fade-out," he said.
"They've got together after the game by themselves which is great, but I won't be letting up in my approach ... when a loss happens like this and last week, there's always consequences."
