Sydney's hard running and pressure cracked Richmond on Sunday, putting a large hole in the Tigers' hopes they can break into the AFL top four.
Brisbane and West Coast also lost on Sunday, joining Adelaide in having their finals chances snuffed out.
Carlton and possibly North Melbourne are now the only teams who could break into the eight with five rounds left.
The X-factor is Essendon's anti-doping investigations, with ongoing speculation that the AFL could strip the third-placed Bombers of their premiership points after ASADA releases its findings.
Essendon will know their fate as early as August 5.
They were the weekend's biggest losers, suffering a nasty combination of on and off-field setbacks.
They dropped from second to fourth and are only half a game ahead of fifth-placed Fremantle following Friday night's 56-point loss to top side Hawthorn.
Bombers chairman David Evans had a health scare in the rooms post-match and then added another stunning twist to the club's anti-doping crisis when he resigned on Saturday night.
Eighth-placed Port stayed a game ahead of the Blues, with North a further two games back in 10th place.
North are equal on points with West Coast, Adelaide and Brisbane but the Kangaroos' season retains a faint pulse because they have a much superior percentage to anyone else in top-eight contention.
In the big game on Sunday, the Swans clinically disposed of Richmond after halftime at the SCG for a 47-point win.
The reigning premiers showed they are on track for September, improving from fourth to third with the 16.14 (110) to 9.9 (63) win.
Richmond remain two games inside the top eight, but face the Hawks next weekend.
The Power scored an ugly nine-point win over Brisbane in windy conditions at AAMI Stadium.
Chad Wingard kicked the only goal of the final term after a controversial umpiring decision against Lions defender Daniel Merrett for the 9.17 (71) to 9.8 (62) victory.
Several weeks of encouraging form finally paid off on Sunday for the Western Bulldogs, who pulled away in the second half to beat the depleted Eagles by 22 points.
The Bulldogs held off a late surge from West Coast to win 16.15 (111) to 13.11 (89) at Etihad Stadium.
Carlton scored their third-straight win to maintain the pressure on the Power, beating Gold Coast on Saturday by 43 points.
North destroyed hapless Melbourne by 122 points, but lost captain Andrew Swallow until next season with an ruptured achilles tendon.
Geelong improved from third to second with Saturday night's 101-point win over St Kilda and the Dockers were good for Adelaide in Perth, beating them by 22 points.
Collingwood's season continues to splutter - they were awful in the first half against winless Greater Western Sydney, but broke clear in the final term for a 40-point win.
The Magpies and fierce rivals Essendon have a massive game next Sunday at the MCG.
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