FROM raging premiership favourite to needing to rewrite history to win the flag.

Sydney's staggering 112-point loss to Port Adelaide on Saturday night continued a dismal run of form which has seen the Swans lose five of their past six games.

The Swans have gone from 13-1 to 14-6 and left needing to set an unexpected record if they are to claim the club's sixth premiership.

Only one premier in VFL/AFL history has suffered a defeat of 100 points or more in the season it won the flag.

That was Carlton in 1945, with the Blues blown away by Essendon at Windy Hill in round three by exactly 100 points.

Unlike this year's Swans, those Blues were 0-3. They would go into the finals on a six-match winning streak before claiming the premiership.

One side handed a belting so late in the season before winning the flag was Collingwood in 1990, with the Magpies rebounding from an 83-point loss to Hawthorn in round 20 of that season. It would mark their last defeat of the year.

In 2004, Port Adelaide suffered a 92-point loss to North Melbourne in round eight. But the Power's road to their one and only flag featured 10 wins in their last 11 games of the home and away season.

Flying high early this season, the Swans lost three of four games by a total margin of five points. Then, the loss to the Bulldogs was "a bit different" for coach John Longmire, who was bewildered by the performance against the Power.

And much like the rest of an unbelievable season, no one saw it coming.