Since then the two rivals have won just three of their next 12 games combined.
When they meet on Sunday at the MCG, Port Adelaide sits fifth and Collingwood ninth.
They've both been sliding quicker than the average politicians' popularity.
Contested ball has dried up.
Collingwood has slipped from fourth in that category in the first 12 rounds to be ranked 15th between rounds 13-18.
Port Adelaide has gone from third after round 12 to be ranked eighth between rounds 13-18.
Both teams have found it tougher to create scoring opportunities from defence.
Collingwood conceded critical goals from stoppages late against Adelaide, beaten for speed away from the contest. Its young defenders were also outmuscled when contesting loose balls late in the game.
Port Adelaide won against Melbourne because it made fewer mistakes in the final minutes than its opposition.
And a statistic that had fallen away since round 12 – creating inside-50s from defensive 50 chains (it was first until round 12 and had slumped to mid table by round 17) – had a positive number added to it with just three minutes remaining when Port Adelaide trailed Melbourne.
From deep in its defensive 50 Cameron Newton kicked to Matthew Broadbent who kicked to Kane Cornes who kicked to Jay Schulz, who upheld his 80 per cent accuracy from set shots with a goal from the boundary.
In a key moment Port Adelaide players trusted each other.
That charging run and spread has dropped off too.
Jared Polec's metres gained per game has gone from 420 to 323. Travis Boak has dropped from 394 to 364. They're just two examples of players who have gone from exceptional to standard in recent times.
Schulz has kept on kicking goals, but the scoring is not being spread. This indicates static ball movement where players hope to (or are forced to) hit a big target rather than having multiple options available and a forwardline creating space for each other.
Port Adelaide averaged 111 points-for between rounds one to 12 and has averaged just 89 points a game since.
In that time Chad Wingard has kicked four goals (28 for the season) and Angus Monfries – who has missed games with injury – has kicked three (12 for season). Robbie Gray (26 for season) has kicked just four (all against Richmond in round 17) and Justin Westhoff (20), forced to play multiple roles to cover the absence of tall defenders, has kicked five. Speedster Matt White (20) has kicked six in that time. He is a big out against Collingwood as the Magpies lack leg speed.
Port Adelaide has also leaked goals at times, missing the dual defenders Jackson Trengove and Alipate Carlile.
Despite keeping a positive inside-50 differential after round 12 – dropping from 13.5 extra inside 50s per game to 4.3 – it has had 85 points kicked against it on average a game, up from 74.5 leading into round 12.
Port Adelaide, like all teams, might preach team defence but individuals, particularly experienced ones, can still make a huge difference.
Collingwood knows that better than most having lost Nick Maxwell to retirement in that period and being without Nathan Brown and Ben Reid for most of the season. Steele Sidebottom's three-week suspension between round 12 and 14 also hurt.
The average contested possession counts of Scott Pendlebury and Dayne Beams have decreased in the past six weeks (Pendlebury from 13.1 to 12.5 and Beams from 12.6 to 11.4). Both have also dropped in average disposals. Sidebottom has gone the other way, increasing his contested ball count and disposals.
Beams returned to his best against Adelaide and Pendlebury always competes at a high standard.
But it's well known Collingwood's midfielders kick fewer goals in losses than wins, and two out of the Pendlebury, Beams, Sidebottom trio need to play very well for the Magpies to win.
Unfortunately for the Magpies it lost critical centre clearances late against Adelaide, but it has been less of a problem since round 12 for the Magpies than it had been from round eight until 12 when the wheels became wobbly.
The inability to score goals has had people lining up to criticise its pressure forwards for not hitting the scoreboard.
Jarryd Blair has been unfairly maligned with his pressure of a high standard (if the Magpies were winning he'd be compared to Hawthorn's Paul Puopolo) and Tyson Goldsack has battled hard.
What happened after round 12 is that opponents started scoring against Collingwood once they got inside 50.
Jack Frost has held up but he has not had the support he requires, particularly as Collingwood had to move its plus one to the stoppage against Adelaide to try to even up the contested ball count.
In four of its five losses since round 12 a key opposition forward has kicked four goals, with Liam Jones, Luke Breust, Sam Day and Jake Carlisle all kicking a reasonable bag against the Magpies. The Pies have not won a second half in that time.
Collingwood's ability to score goals has been an issue for two years, but its defence looked solid under Nathan Buckley from about round 10, 2103 until round 12, 2014 when it only conceded on average 74 points a game.
Since then it's conceded 96 points a game, unable to hang tough for 100 per cent of match time.
"The opportunities are there for us to show more composure and more poise at the appropriate moments in games, sometimes it's showing more grunt at the appropriate times," Nathan Buckley said on Wednesday.
Tired, injured and not getting the same protection from its midfield, the Magpies have wilted.
But with a defence that includes Frost, Lachlan Keeffe, Tom Langdon, Marley Williams, Paul Seedsman and, when he returns from injury, Ben Sinclair, all having played fewer than 50 games, the signs are very positive for Collingwood's future.
In the medium term Collingwood needs to develop good kicks out of defence and get some speed in through the draft. Ben Kennedy and Tim Broomhead look quick and talented while Matt Scharenberg – who won't play senior football this season – and Nathan Freeman wait in the wings.
The free agents it has added haven't compensated in the short term for the talent it lost, but the decisions will reap benefits in the medium term.
The return of Monfries and Carlile will help Port Adelaide bounce back.
Its fighting win over Melbourne – when it looked beaten with three minutes remaining – should be a unifying victory.
Port Adelaide is a contender. Collingwood will be at some stage under Buckley.
Right now both teams are experiencing growing pains.
| COLLINGWOOD | PORT ADELAIDE | |||||||
|---|---|---|---|---|---|---|---|---|
| R1-12 | Rank | R13-18 | Rank | R1-12 | Rank | R13-18 | Rank | |
| Contested possession differential | +5.4 | 4th | -9.8 | 15th | +5.8 | 3rd | +0.3 | 8th |
| Inside-50s/game | 51.2 | 7th | 49.0 | 10th | 56.8 | 1st | 55.8 | 3rd |
| Inside-50s differential | +0.6 | 10th | -1.3 | 11th | +13.5 | 1st | +4.3 | 7th |
| Points for/game | 87.8 | 8th | 78.5 | 14th | 111.2 | 2nd | 89.3 | 7th |
| Points against/game | 71.9 | 3rd | 96.3 | 15th | 74.5 | 4th | 85 | 10th |
| Centre clearance differential | -1.5 | 14th | +0.2 | 9th | +1.1 | 5th | -0.5 | 13th |
