The AFL has admitted that the free kick paid against Bomber Will Snelling for a dangerous tackle - which led to goal to Collingwood's Callum Brown in the final quarter - was wrong.

The AFL said on Saturday that the dangerous tackle free against Snelling was "unwarranted'', the umpire having thought that Brown's arm was pinned and the tackle excessive, leaving Brown vulnerable.

The free resulted in a goal that helped the Magpies cut Essendon's lead, which was eventually whittled from 27 points to just three with several minutes left before the Bombers steadied and won by 15 points.

"The AFL confirms the dangerous tackle free kick (to Brown) was unwarranted,'' an AFL spokesperson said.

"In the umpire's view, he thought one arm was pinned and the tackle was excessive which left the head in a vulnerable position.''

The game also contained a contentious and unusual goal umpiring decision, or situation, when a shot from Collingwood's Jordan De Goey hit the goal umpire and then hit the post, when it might have crossed the line, if not for the umpire contacting the ball. On score review, the shot was declared a behind because it was found not to have crossed the line at the point when it hit the umpire.