AFL UMPIRES don't 'single out' players who have a reputation for playing for frees, according to field umpire Jacob Mollison.

High tackles awarded to players dropping their knees has become a major talking point this season, with Hawthorn great Dermott Brereton going as far to say the practice had become a blight on the game.

The furore led North Melbourne coach Brad Scott to declare Lindsay Thomas had become a "poster boy" for the issue after the forward received two free kicks for high contact against the Swans on Friday night.

Mollison, who has umpired over 150 AFL games, said both decisions were correct, despite in one instance Thomas lowering his knees and pushing his head back into a Nick Smith tackle.

"These examples are clear high tackles, (because) watching them in real time I think every umpire on our list would pay those," Mollison told AFL.com.au's Whistleblowers program.

"(The umpire) in those two scenarios saw the high contact and paid the free kicks.

"We are coached in that way to pick up those free kicks as a high tackle."

When asked if umpires kept a close eye on players with a reputation for the practice, Mollison said the pace of the modern game didn't allow for discrimination.

Players such as Lion Allen Christensen, Bulldog Toby McLean and Geelong skipper Joel Selwood head the list of recipients of head-high frees in 2016.

"You're not really too mindful (of them), because it does happen so quickly," Mollison said.

"There's a split second decision you have to make, and it really does happen too quickly to single out any particular player.

"We don't want to single players out; we want to umpire every decision on its merit."