FREMANTLE coach Justin Longmuir says he will worry about his ruck puzzle next week after big man Mason Cox took his chance on Thursday night and produced his best game for the club in a powerful win against Sydney.

Cox was called up for his first game since round 15 after Sean Darcy was managed on a five-day break, rising to the occasion with a terrific display of contested marking at Optus Stadium that was topped off with a critical final-quarter goal. 

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Longmuir said Darcy would have played on a seven-day break, but the club chose to manage him and not risk aggravating a troublesome knee by fielding him for a third game in 12 days. 

The coach paid tribute to Cox's performance and said a selection decision between the Collingwood premiership player and Darcy for next Saturday's clash against Port Adelaide was something he'd worry about next week.  

"I thought it was the best he's marked the footy, and I thought his ruck work was strong," Longmuir said. 

"'Jacko' (Luke Jackson) and (Brodie) Grundy were having a real good battle and he came on and had a real impact when he came on. It was probably his best game for the club. 

"Everyone really needs to earn their spot in the side, don't they? So we've got competition for spots, not just in the ruck, we've got competition for spots all over the ground.

"He got his opportunity tonight and came on and performed his role. So it's healthy competition for spots. It keeps everyone on edge and preparing really well. 

"Our rucks are probably a bit the same."

Fremantle kicked 0.11 in the first half and went goalless to the main break for the third time in its history before kicking 100 points in the second half and blowing the game open with a nine-goal final term. 

Longmuir said he kept faith that the scoreboard would turn if the Dockers stuck to their guns, with the coach proven correct.  

"I thought our second quarter in particular was strong without hitting the scoreboard as much as we like, but it's about process," the coach said. 

"Law of averages will say that you're not going to kick 0.22 for the game, so you've just got to keep maintaining faith in the process and the plan that we went in with, and eventually the scoreboard will look after itself. 

"Once we got the crowd into it, it becomes quite daunting I would imagine for the opposition, and the floodgates open with the amount of field position we were getting."

After a loss against Greater Western Sydney last week that he labelled as their worst in years, Longmuir said he was proud of how his team owned the performance and handled the five-day break.  

Captain Alex Pearce led from the front come Thursday night, constantly supporting his backline teammates in the air and taking an inspirational goal-saving mark running with the flight in the final term. 

"He doesn't second guess himself, does he? There's no situation he doesn't want to be in, so he's led by example all year and he just continues to do it," Longmuir said. 

"I thought he was terrific. He played with the right mindset … and led from the front.

"Whenever you see a back leading his man to the ball, you know they've got good positioning, and they're reacting quicker than their opponent, and I thought he did that from the outset."

Both teams received free kicks on Thursday night for taunting, with the Dockers giving up a goal in the first quarter after Luke Ryan rubbed the head of Chad Warner after the star midfielder missed a set shot. 

In the third quarter, Jye Amiss received a reversed free kick after Dane Rampe did the same, with both Longmuir and Swans coach Dean Cox keen for their players to avoid taunting opposition players. 

"It's clear. The AFL said it's clear. Maybe we could have educated our players a little bit better on that," Longmuir said.

"I haven't seen it in the game for months, so for two to happen in one night is a bit odd. 

"But the AFL has made it really clear that you can't do it. So why do it?"