Monfries staged a running battle with fiery Collingwood defender Heath Shaw during the elimination final clash at the MCG which Port won 12.15 (87) to 9.9 (63).
The second quarter was one embarrassing incident after another for Shaw, who looked on in frustration as Travis Boak kicked a goal for Port in the opening minute. Shaw immediately lashed out at Monfries, who was getting in Shaw's ear.
Monfries was awarded a free kick and Port were given a shot at goal from the goalsquare which Monfries converted to put Port ahead by 18 points.
A furious Shaw paid no attention to the Collingwood runner who came out to offer advice, as the 2010 premiership player turned his back.
By halftime the visitors led by two goals and Shaw's anger had not faded, as the Collingwood defender threw the ball in the face of Monfries moments after the halftime siren.
Port's high-profile president and TV personality David Koch threw his hands up in frustration in the stands, perhaps wondering why another free kick wasn't awarded to Monfries.
Shaw's anger was still evident at the 13-minute mark of the third term when he executed the perfect tackle at half-forward against Port's Matthew Broadbent but the act went unrewarded by the umpire.
A minute later, the Collingwood fans were in full voice again as you guessed it, Monfries received another free kick.
Shaw started the last quarter opposed to Robbie Gray and later Hamish Hartlett and Monfries was picked up by Marley Williams.
The Magpie Army was thrilled when Monfries outmarked Williams, played on and missed with a snap at goal as Collingwood clung to a three-point lead at the 10-minute mark.
Monfries' fellow small forward Chad Wingard, with a goal and a goal assist to finish with three goals, dominated the final quarter in the key moments for Port.
But for Monfries, who leapt in the air in delight at the final siren, the joy of being part of Port's fairytale win over Collingwood was enough satisfaction to add to his one-goal, 15-disposal performance.
For Shaw, who has tasted the highs and lows of finals football, it's all over for another year after having just 11 touches against Port.