Lindsay Thomas was the catalyst behind North Melbourne’s 35-point win over Richmond on Saturday, coach Brad Scott says.

Thomas kicked four goals in the second half, including three in a vital third term when the Roos asserted their dominance.

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Helped by a stand-out contribution from veteran forward Drew Petrie, the Roos booted seven-goals-to-one during the third term and Scott singled out his team’s ability to "keep our emotions in check” as a key factor in the win.

"After some really disappointing lapses in concentration and some poor discipline late in the second quarter we were able to respond and keep our emotions in check and take out any frustrations we had on the scoreboard," he said.

"No one really demonstrated that better than Lindsay Thomas. He was the one who got us going after half-time after a disappointing second quarter."

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While Thomas stayed closer to goal and feasted on opportunities brought about by regular Richmond turnovers, Petrie provided much-needed direction for the Roos up the field and finished with 21 disposals, 10 marks and a goal to earn special praise from his coach.

"He played a little bit higher just because of the conditions and the opposition dictated that," Scott said.

"It was clearly his best game of the year. You look at his tackling and defensive pressure, he really led the forward line today.

"It’s great to have Drew playing with that intensity because it makes five or six other players in our forward line walk a lot taller when he’s doing that."

Despite leading throughout, the Roos were unable to pull away from Richmond until after half-time, leading by just six points at the long break.

But through persistence, sustained pressure and more direct football they crushed Richmond’s resistance after the break and had the game in the bag by three-quarter time.

"It looked like being one of those really tight, potentially scrappy, congested, contested sort of games," Scott said.

"The longer the game goes on, if you can keep persisting, players get tired and the pressure drops a fraction and you are actually able to go forward with a bit more effectiveness."

With Essendon at Etihad Stadium and a trip to Fremantle coming in the next fortnight, Scott was under no illusion as to how hard his side will have to fight to improve on its 3-3 record.

"The competition is so tight … every game is hard and people think coaches say that flippantly (but) I don’t see any easy games out there. I see every team having to earn the four points," he said.

"It was important to get back to three-and-three today and we’ve got plenty of improvement in us. At least we’re still in the mix, we’re still in the race."

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