SYDNEY Swans coach John Longmire is demanding a return to his team's trademark high-pressure style for their historic Anzac Day clash with St Kilda in Wellington.

But the reigning premiers are expecting to be without valued utility Lewis Roberts-Thomson for several weeks as he is scheduled for arthroscopic surgery after damaging his knee in Friday's 21-point home loss to Geelong.

The Swans flew out from Sydney on Monday morning with a squad of 26, including midfielder Jed Lamb, who is yet to play a senior game.

Longmire was resigned to losing Roberts-Thomson for a period.

"He'll have what we hope is a minor operation on his knee and have a bit of a look to see if there's any cartilage damage," Longmire said at Sydney Airport.

"Hopefully, there's not too much there and he'll be back in a few weeks."

The coach was philosophical about losing another experienced player down back after previous injuries to Alex Johnson and Rhyce Shaw.

"We've seen Dane Rampe come into the team, so he'll get an opportunity to play, Tony Armstrong is playing a bit more," said Longmire.

"What happens now is that they get more of an opportunity to play."

After the Swans had their unbeaten season start halted by the Cats, Longmire had no doubt about what his team needed to focus on against St Kilda in the first AFL match for competition points to be played outside Australia.

Against Geelong, the Swans made just 47 tackles - their lowest tally since 2010 - and conceded 124 points, more than in any game of their 2012 premiership-winning campaign.

"I think it's very simple. We've got to get back to the trademark style of footy for four quarters that we know we can play," Longmire said.

"We lost the one quarter on the weekend and we had seven goals kicked against us in that one quarter.

"That's a direct reflection on not being strong enough for that period of time in our pressure acts.

"Our ability to be able to tackle was disappointing. It's something we spoke about straight after the game and something we need to focus on."

While St Kilda has lost three out of its four games and are coming off a 37-point defeat by Essendon, Longmire said their best was still very good.