SYDNEY coach John Longmire has questioned the consistency of the AFL's Match Review Officer after defender Robbie Fox was diagnosed with delayed concussion.

Fox failed a head injury assessment after being collected high by Mitch Duncan late in the third quarter of the Swans' humiliating loss to Geelong on Saturday night.

Duncan escaped penalty for the Fox hit, with the Match Review Officer finding his actions "were not unreasonable in the circumstances".

Fox's absence from Saturday afternoon's Sydney Derby against GWS accentuates the Swans' issues in the key defensive posts with Paddy McCartin still sidelined with concussion, while his brother Tom and captain Dane Rampe are no certainties to return against the Giants.

Lance Franklin remains in doubt as well after missing the last fortnight with a knee problem.

While Longmire agreed that not every hit to the head should incur a suspension, he outlined his confusion with the MRO's findings.

"We lost Franklin after week one under circumstances where we thought he was trying to protect himself," Longmire said.

"He was suspended, so just a little bit of consistency, but we also understand that not every incident where players get knocked in the head is going to be suspended either," he added.

It's a further frustration for the Sydney coach off the back of the 93-point hammering from the Cats, which is Longmire's heaviest defeat in his 289 games in charge of the club and the Swans' largest in 25 years.

"It doesn't sit very well with any of us," he said.

"Regardless of player availability we've just got to find ways to deal with that and getting on with it and focus on the competitiveness and the contest," he added.

The Swans also went goalless in the second half for the first time since 1977 while the loss follows on from the 81-point defeat to Geelong in last year's Grand Final.

"We can't lose the contest by as much as we did on the weekend and in the Grand Final and expect to be competitive. We haven't been up to scratch with our intent in those two games," he said.

A major talking point out of the humiliation at Kardinia Park was the decision to play All-Australian midfielder Callum Mills deep in defence while key-position recruit Aaron Francis played as a forward.

"We lost Joel Amartey last week, so we needed a key forward, we need key backs, that's just the situation we're in," Longmire said. 

Mills has been swung into defence at times recently since becoming one of the premier ball-winners in the competition, but the exclusive nature of his defensive role on Saturday night has surprised Swans' fans despite the club's availability issues.

"At different times you need senior players down there to help with that, we'd rather not play him there, but we needed to on the weekend," Longmire said.

"We'd love him to play in the midfield but if we played Francis and (Will) Gould as full-back and centre half-back, who plays forward for us?

"When we have injuries to our key defensive stocks there's a reality of trying to manage that we're trying to get on top of."

The return of either Rampe or Tom McCartin would be most welcome for the Swans this week but Longmire sounded less than optimistic ahead of the big clash with the Giants.

"We'll see how the week progresses, we're hoping they'll do a bit more training than last week. Ultimately, they'll be assessed by the doctors, it won't come down to 'Foxy' not playing, it'll come down to whether they're ready to go," he said.

Longmire also stopped short of guaranteeing a return for ruckman Tom Hickey after he played in the VFL last week, considering the 32-year-old's poor soft tissue injury record of late.