PORT ADELAIDE was dealt a lesson in pressure football by a desperate North Adelaide at Alberton on Saturday afternoon when the sixth-placed Roosters scraped to a slim victory late in the final quarter.

The momentum swung for most of the afternoon and despite the Magpies leading at every change, it was the Roosters who remained calm under pressure to run out eventual winners with a four-goal-to-one final term.

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The loss soured Port captain Steve Summerton's 150th match, but the skipper stayed true to his consistent form this season with 22 touches and one goal.

Things looked much different little more than an hour earlier, with the Magpies responding to the first Roosters goal by kicking the next five.

Lewis Stevenson impressed with his rebounds from defensive 50, and combined with Irishman Daniel Flynn's pace off half back to create Port Adelaide's trademark free running game and offer plenty of options in attack.

Despite leading by 19 points at the first change, thanks in part to the efforts of small runners Karl Amon (two goals), Jake Neade and Jake Johansen, the Roosters clawed back into the contest with a flurry of goals in the second term to level the scores on the cusp of time-on.

John Butcher and Ben Newton pushed the margin out again before half time, and the Magpies again took advantage of their opportunties in the third quarter despite North leading in most key areas.

And yet every time the Magpies threatened to break away, the Roosters refused to give in - booting two goals to close the margin again before Harvey and Summerton kicked away for the home side once more.

But the Roosters wrest the momentum back again and this time took control of the game, levelling the scores early in the fourth quarter and hitting the lead for just the second time when Ryswyk slotted his fourth.

Ben Newton again found the goals to give the Magpies hope, but a late charge from the Roosters rushed one and scored two crucial behinds to edge Port at the post and claim an important upset.

The Roosters needed to win leading into the game in order to keep its finals hopes alive and the red and white were given plenty to crow about after Norwood - their closest rivals in the top five - succumbed to the Eagles at Woodville Oval in the simultaneous match.

For Port Adelaide, the loss and parallel wins to the Eagles and Sturt means it clings to a narrow one-match lead atop the standings, with five huge tests to come after next week's bye.

Things get interesting with the first ever SANFL 'Showdown' at Alberton Oval on Saturday 26 July against the in-form Adelaide Crows.

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