COLLINGWOOD coach Craig McRae kept his cards close to his chest regarding his boundary-line exchange with Brodie Grundy during the Swans' six-point victory over the Magpies on Friday night.

"I would love to be able to share, but I can't share exactly what I said to him," McRae said post-match.

"It was all respectful, trust me, and I've got great respect for him ... there was nothing untoward."

But while the coach remained tight-lipped, nobody told Grundy he had to keep the secret.

"He just said, 'Good day, old mate'," Grundy told media in the rooms after the game.

"He's bugged up. He can be a bit quirky at times, Craig. So, it's a bit like, 'Hello'. 

"That was nothing untoward. I think he was just trying to take me off my game."

In the wet, Grundy delivered a Goodes-O'Loughlin Medal-winning performance that acted as a pressure valve for the Swans, physically wearing down an undersized Magpies outfit to inspire a sensational second-half fightback against his former side.

Dominating the air and the ground to drive the Swans forward, he finished with one goal, 34 disposals, 12 clearances, and 46 hitouts — spearheading Sydney's devastating third-quarter blitz.

By outworking his opponents at the stoppages and winning the hard ball at ground level, Grundy proved to be the difference-maker, extending the ladder-leaders' winning streak to seven.

The performance came at a time when the Magpies were already undermanned, without No.1 ruck Darcy Cameron due to an ankle injury, which left the bulk of the duties to eight-gamer Oscar Steene.

However, the young tall's night ended prematurely when his left knee buckled awkwardly during a third-quarter contest. Visibly distressed, he was helped straight to the rooms by medical staff, with scans on Saturday confirming a season-ending ACL injury.

Steene's exit left Collingwood without a recognised ruck on the field, forcing McRae into a major tactical reshuffle. 

Undersized players were thrown into the air to compete, with key forward Jack Buller, key defender Billy Frampton and midfielder Ned Long rotating through the role, but none could contain an in-form Grundy. Ultimately, the primary burden fell on key forward Dan McStay, who was thrust into the middle.

The mismatch proved decisive, with Grundy acknowledging that the Magpies' makeshift ruck setup played into his hands.

"You can only play on what your opposition is, what's in front of you," he said.

"So, I just try and, irrespective of what the name is, stick to my process.

"I just want to feel like I'm playing my brand of footy, which is obviously the ruck work, but then following up at ground level. So, I thought I did that well.

"Obviously, you're rucking against some of their midfield players, so you've got to acknowledge that. 

"I was a bit disappointed with my application to that (against North Melbourne), so I just wanted to get my feet going and get my follow-up game going. I thought that the conditions probably helped me to do that, so that was nice."

Swans coach Dean Cox praised Grundy's effort and highlighted how he tactically took control after Steene went off injured.

"He was really good again," he said post-match.

"Once (Steene) got injured, Brodie started to gain a little bit of ascendancy against some of their key forwards. I thought he was clever in between (choosing) whether to try and clear the area or to connect with a midfielder – his variety in that was really good."

Despite his dominance, Grundy was deeply impressed by Steene and offered his well wishes after the "disappointing" incident.

"My best wishes to him (Steene), he's a great young talent," Grundy said.

"I've been watching him all year. He was giving me a few headaches there in the centre bounce – he can jump through the roof."

Having featured in every match for Sydney so far this season, Grundy dismissed any suggestion that he was due for a rest.

"I felt good," he said.

"(Against North) I was a bit flat. So, I got myself up and about.

"It's obviously a big game, playing against Collingwood, Marn Grook at the SCG, Friday night footy. It's hard not to get up and about for an occasion like this.

"We had our past players come into the football club this week, our First Nations players. We also went off-site to the NCIE (National Centre of Indigenous Excellence) for some cultural immersion, connection, and celebration, so it was a beautiful week."