Sydney coach John Longmire was left disappointed after Tom McCartin was floored by a heavy hit during the high-flying Swans' emphatic 29-point victory over Greater Western Sydney on Saturday.

McCartin was ruled out of the Sydney derby after Giants forward Callum Brown made high contact with a bump on the Swans key defender in the second term of the clash at the SCG.

The 24-year-old slumped to the turf and was soon seen with a large bump under his left eye before undergoing a head injury assessment and being subbed out of the match.

McCartin was sidelined for several matches last year after suffering a concussion against Port Adelaide in round four.

The full-back initially sat out a pair of matches, then returned to play two games before being sidelined for an extended period when experiencing headaches linked to the earlier concussion.

Longmire was tight-lipped on what the latest head knock might mean for McCartin, whose brother Paddy was forced into retirement last year due to the ongoing effects of multiple concussions. 

"Let's just wait and see what happens. It's disappointing to lose him, he's a very important player for us," Longmire said.

"But you'd expect him to miss this week, and we'll see what next week brings.”

The Giants made a fast start to lead by 15 points at the first change, but the Swans edged ahead until forward Will Hayward burst the game open with three goals in the third term.

Hayward finished with an equal career-high four majors to with Longmire praising the forward.

"He's a threat in the air but also a threat on the ground," Longmire said.

"He applies enormous pressure, he chases out so well and when the ball hits the deck hopefully makes the opposition a little bit nervous and he gets after them.

"He's got great speed and he's been able to hit the scoreboard this year, which is good."