The Swans have won just once in their last seven games, virtually ending their chances of a seventh consecutive finals campaign.
The 15th placed Demons, on the other hand, are two wins from three with some exciting young players starting to emerge.
Longmire said Friday's main training session, the last before Sunday's clash at Manuka Oval, will focus on ball use and core defensive aspects of the Swans' game.
"We were a bit sloppy with our ball use last week and Carlton was good with theirs, so it was a two-fold effect and they made us pay," he said on Friday.
"We've got to get our general work rate across the board a bit better and make sure we work together to close down their better ball users and get our blokes out in a bit of space.
"It's about a more consistent four-quarter performance and making sure our defensive aspects are right. It's been a real strength of ours over the years."
The Swans have named youngster Dan Hannebery for his second senior outing after an encouraging performance against Carlton last weekend.
Jarred Moore, Kristin Thornton, Amon Buchanan and Mike Pyke have also been named in the extended team for the clash.
Longmire is not underestimating the Demons.
"They've been in reasonable form over the last month. And some of their younger players in particular have shown some real life, such as Liam Jurrah who's been a real livewire and obviously a very clever player," he said.
"Bate's another one who's playing some good footy and Bennell's come into the team. He's another good young player who's playing a role.
However, missing for the Demons through injury will be experienced midfielder Brad Green (fractured wrist) and ruckman Mark Jamar (quad). Also out is forward Russell Robertson, further clouding his future at the Dees.
"We've just got to make sure that we take our chances when we can," Longmire said.
"There was disappointment about fading out against Carlton last week and we've spoken about that this week."
