SYDNEY Swans midfielder Dan Hannebery will be sidelined for around a month with a torn ligament in his ankle, suffered in Saturday's four-point victory over Port Adelaide, the Swans' eighth in a row.

Hannebery's absence may see veteran Ryan O'Keefe in line for a recall to face Richmond this week.

Mike Pyke has made it through two games in the reserves following a hamstring injury and would be a likely reinforcement against the Tigers, with fellow ruckman Tom Derickx showing signs of fatigue against Port.

First round draft pick Zak Jones (who was an emergency in round 13) Shane Biggs and Tim Membrey are among those also showing some good form in the reserves, while O'Keefe has been toiling away in the seconds since being dropped heading into round five.

A Norm Smith medallist, club best and fairest and former All Australian, the 33-year-old O'Keefe has been out of favour during the club's successful run, with Harry Cunningham and Jake Lloyd among those moving ahead of him.

Coach John Longmire was reluctant to speculate about possible replacements for Hannebery on Monday, but the 286-game veteran would have to be in with some chance.

"There's been a few players," Longmire said when asked who was performing well in the seconds.

"I don't want to throw any names around today because all of a sudden they're the ones that get in.

"We haven't had time to sit down and work through that yet and we'll do that in the next two days.

"We've got a number of blokes there that we can bring in that we think can help us win.

"The reality is you need about 35 players to get through a season and that's why it's important for those blokes in the reserves to keep in good form, because you never know when you'll get your chance.

"It opens up when you least expect it and that's why you've got to be in good form when you get those opportunities and grab it with both hands.

"We'll sit down in the next 24 to 48 hours and work out what the replacements are."

The exact timeframe for Hannebery's return is not yet known, with Longmire saying it could be more or less than the four weeks initially diagnosed.

Hannebery was kept quiet by Port tagger Kane Cornes on Saturday, but had previously been in the type of form that led to his first All Australian guernsey last year.

While a replacement needs to be identified in the short term, Longmire is also looking for some of his youngsters to lift to help fill the considerable midfield void.

"Probably since the first month when he was a bit quiet he's had a really solid season and back to where he was last year," Longmire said of Hannebery.

"He was a bit quiet on the weekend, but prior to that he's been one of our best midfielders.

"But he's out now and we've been fortunate we've been blooding some extra midfielders through that area, Cunningham and Lloyd and players like that have been playing pretty well for us.

"They just get more responsibility."

Twitter: @AFL_JD