Hawthorn's Shiels hamstrung in AFL

A hamstring injury means three-time premiership player Liam Shiels is out of Hawthorn's side for the AFL blockbuster against Sydney.

The frontline midfielder will be sidelined for up to a month after suffering the injury in last week's rugged win over Port Adelaide.

The Hawks were initially hopeful it was only tightness, but scans were worse than expected.

"It looks like he has a regulation three- to four-week hamstring," said Hawks football manager Chris Fagan.

"So it's a no-risk approach.

"We were hopeful for a better result than that."

Shiels has played 13 games this season after missing the first two rounds with a wrist injury.

Jonathan O'Rourke, whose last senior game was in round three, is shaping as Shiels' replacement.

Shiels' absence will be another test of player depth for the three-time defending premiers, who are without star forward Jarryd Roughead indefinitely as he undergoes cancer treatment.

Captain Luke Hodge has also made a successful return from knee surgery.

The Hawks are a game clear on top of the ladder after six-straight wins and again are rated the team to beat for the premiership.

But the second-placed Swans are also coming off an outstanding win in Geelong against the Cats.

Hawks small forward Paul Puopolo said there was plenty of room for the Hawks to improve.

"We don't think we're playing good enough footy to win finals - we think we need to get better," Puopolo told RSN.

"Sides like Sydney and Geelong, their best footy is really good.

"We want to make sure we're able to play at our best when we need to play at our best and we just think we're not quite there yet."