HAWTHORN coach Alastair Clarkson will caution his players against breaching the protected area after watching Richmond concede five free kicks under that rule on Thursday night.

Before the start of the home and away season, the AFL foreshadowed umpires would strictly enforce the protected area of eight-to-10 metres around the mark. 

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That proved to be the case in the season opener between the Tigers and Carlton, with the reigning premier repeatedly penalised after its players entered the protected area, several of those free kicks resulting in easy goals to the Blues. 

Clarkson told reporters on Friday the umpires' strict enforcement of the protected area on Thursday hadn't been unexpected, but said he would again address the rule with his players before their round one clash with Collingwood on Saturday night. 

"It always is [enforced strictly] early in the year and then it seems to taper off a little bit, so the really interesting part is just whether that's maintained over the course of the season," Clarkson said.  

"We're obviously mindful of that and need to educate our players a little bit, just making sure that they're wary of an infringement being incurred because it's a significant penalty. 

"As we saw last night, Richmond infringed on about six occasions and I think three or four of them ended up being easy goals from the top of the goalsquare.

"That has a pretty significant impact on the scoreboard, so we have to be mindful of that."

Port Adelaide coach Ken Hinkley also spotted the tight interpretation of the protected zone on Thursday night.

"It did look very hot, didn't it? We're aware of it and we take notice and we try and make sure we don't infringe in areas of the game that the rules say you shouldn't," Hinkley said on Friday morning.

"The AFL have been really clear during the summer through Steve Hocking that they were certainly looking to protect that area, as it's supposed to be. We look forward to using the opportunities to take that area on.

Hinkley said the issue had been raised when the umpires visited his club a fortnight ago.

"They basically made a point that they were going to umpire that area a little bit closer. Perhaps, they thought as last season unfolded they went away from a little bit is what they would say themselves," he said.

"At the start of the season, they're going to be right on top of it."

St Kilda coach Alan Richardson briefed his players before training on Friday to be wary of the tighter interpretation of the rule.

"It was probably adjudicated a little bit tougher than it had been in JLT, so it probably took particularly the Tiges by surprise. We had a bit of a chat about it with our guys in the meeting pre-training," Richardson told reporters on Friday.

While he likes the change, the rule was officiated too harshly for Richardson's liking.

"We'd been told by (umpires coach) Hayden Kennedy that was going to be a real focus, to keep the game flowing. They wanted to free up that area of the ground but there were a couple that were probably a little bit over the top," Richardson said.

Geelong coach Chris Scott sympathised with the umpires and said the tight interpretation was probably linked to its early-season timing.

"The umpiring department definitely did a good job of covering that off with the players and coaches in two separate meetings," he said. 

"I think the competition understands why it’s in, but it’s just such a heavy penalty when effectively if it’s your forward half, generally it ends up costing the opposition a goal.

"One positive of playing late in round one is that you get to see the other games.

"Sometimes I think we overlook the fact the umpires are a bit nervous. Round one is traditionally really hot around the ball early, error-riddled and the players are exhausted towards the end. I tend to think the umpires are a bit the same."