Heeney (ankle) and co-captain Kennedy (knee) both failed to see out Sunday's eight-point defeat to Richmond in a dour slugfest at the Gabba.

The latest injuries are a hammer-blow for Sydney ahead of their round-seven meeting with Gold Coast at the SCG next Saturday.

"Josh has done a medial (ligament), so he'll miss a number of weeks," Longmire said post-match.

"It was pretty bad, and Isaac's still being assessed so I've got no idea at the moment.

"It was obviously a pretty bad ankle because he's pretty tough.

"He wouldn't come off normally unless it's pretty bad."

The Swans already have a long list of players on the sidelines, with their tall stocks dwindling alarmingly.

Superstar Lance Franklin and fellow key forwards Sam Reid and Tom McCartin are all out of action, as is first-choice ruckman Sam Naismith.

Defender Lewis Melican and back-up ruckmen Callum Sinclair, Michael Knoll and Joel Amartey are also in the sick bay.

"We need some players back and that helps with a bit of structure and it helps with a bit of system," Longmire said.

"We lost another two tonight and Isaac's one that can give you a bit of shape in front of the ball.

"We had some lighter bodies playing tonight, there's a few younger fellas playing and hopefully we'll get some players back soon."

Despite their lack of available talls, the Swans made a surprise decision to drop 195cm key defender Aliir Aliir from the team that took on Richmond.

"(Aliir) just hadn't been playing very well and he hasn't been playing to the standard that he likes to," Longmire said.

Australian Associated Press