THE AFL has ticked off the controversial free kick paid against Collingwood wingman Tom Phillips for contact below the knees against West Coast forward Jamie Cripps on Saturday night.

However, it conceded an error was made in penalising St Kilda left-footer Jack Billings when he attacked the footy and collided with Fremantle youngster Adam Cerra the following day.

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Geelong premiership coach Chris Scott is one who believes there needs to be "really strong debate" over the rule.

The rule that disallows forceful contact below the knees was brought in after then-Sydney speedster Gary Rohan suffered a gruesome broken right leg when then-North Melbourne forward Lindsay Thomas slid into him in 2012.

Umpires coach Hayden Kennedy clarified why the Phillips decision was correct in an video.

"We see the Collingwood player elect to go to ground, and what the umpire then has to make a decision on is to whether or not he's responsible for forceful contact made to the opposition player," Kennedy said.

"Our belief in this one is that he's responsible."

Billings, however, was unlucky.

"That shouldn't have been paid. Billings has attempted to mark, he's on the ground, he reaches out, so it shouldn't be any forceful contact below the knees in that circumstance," Kennedy said.

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Kennedy explained the difference between the two.

"(Billings is) actually on the ground. The one beforehand with Phillips, he elects to go to ground and make the contact," Kennedy said.

Scott, who was seemingly unaware of Kennedy's comments, told AFL 360 the decisions were incorrect.

"My understanding is they are saying 'you're right, they're mistakes'. Is anyone saying no? Because I think that's where we should have a really strong debate as an industry, when the AFL comes out and says 'no, no, we're happy with that'," Scott said. 

"Every indication I've got is they're saying 'no, no, that's not right, that's a mistake'."

It came after Cats superstar and AFL Players' Association president Patrick Dangerfield lashed the Phillips decision on Twitter.

Gold Coast coach Stuart Dew believes players know how to draw frees.

"I think players, like all free kicks, have worked out how to milk a little one," Dew said.