Collingwood forward Mason Cox has been fined for his bump on Western Bulldogs' defender Jason Johannisen that saw him reported for rough conduct in the last quarter of the Friday night game at Etihad Stadium.

The 210-centimetre Magpie run into Johannisen when he had his head over the ball as he tried to pick it up.

However the AFL's match review officer Michael Christian assessed the incident as careless, head-high contact with low impact.

Johannisen received a free kick in the incident that happened late in the game but he continued to play.

Magpies' coach Nathan Buckley had defended the American-raised former basketballer who made his debut in 2016.