Franklin tweaked his right knee against Adelaide in round three and subsequent tendinitis has kept the Swans' boom recruit from training fully since.
He landed on it again on Saturday night and hobbled from the ground before being handed the red vest in the third quarter.
Longmire said the injury wasn't serious and expected his superstar forward to line up next week against the Brisbane Lions at the Gabba.
"The physios are quite confident that he'll be able to play next week and that's all I can go for at the moment," Longmire said.
"It's been a bit sore ever since [the Adelaide game], there's a little bit of tendinitis in front of his knee and he jarred his 'fat pad', the physio said before, that's more than likely what it is.
"He hasn't done much training since that game … and that's what he's jarred again tonight.
"It has been settling down ok and that's one thing we're hopeful for this week."
The knee is the same one he hurt in the 2011 qualifying final against Geelong and was believed to have required careful management since.
He has periodically missed games as a result, including the Indigenous All Stars game in February last year.
But Franklin appeared unperturbed by Saturday night's tweak as he tried to prove his fitness before the medical staff ruled him out of the game.
He was also seen to be in good spirits in the rooms following the Swans' third win for the season, as he iced the knee.
Longmire said the flare up was not concerned with the original 2011 injury that happened when he dramatically hyperextended his leg during the finals.
"It's unrelated; he just landed on his knee in the Adelaide game," he said.
"He landed on it pretty early and he was able to play pretty well in that game, he played really well in the second half last week so he's still able to play at a certain level.
"He just runs the risk occasionally of it flaring up, which it did tonight.
"We've just got to be mindful he's not doing a heap of training for us at the moment on the ground, he's working really hard off legs but not a heap of training.
"We need to get him right at some point but how long that will last I'm not too sure."
Franklin had a night – and week – to forget.
He kicked one goal against the Demons from a free kick and failed to touch the ball in the second quarter.
Longmire said it was hard to know if Franklin's Wednesday night accident that saw him damage his girlfriend's Jeep plus four parked cars had played on his mind, but expected it was more his knee that had affected his output.
Franklin also engaged in heated exchanges with a range of Demons including opponent Tom McDonald, Alex Georgiou and even co-captain Jack Grimes.
"I don't know, they might have had something to do with that as well," Longmire said.
"I couldn't tell you what was said between the players or who instigated it.
"He's been a little bit sore so in the end it wasn't an ideal week for him, let's not shy away from that. It's not ideal but that's what you deal with and he's got to be able to make sure he [can] switch on to the footy."
Longmire said Lewis Jetta corked a calf and expected him to recover.
