EMERGING Geelong star Mitch Duncan will struggle to return before the end of the home and away season after scans confirmed he has broken the fifth metatarsal bone in his right foot, leading sports medico Dr Peter Larkins says.

Geelong announced on Monday afternoon that Duncan would have surgery to repair his foot and – in a massive blow to the Cats' finals hopes – would be sidelined for 10-12 weeks.

Larkins told AFL.com.au that if Duncan had a smooth rehabilitation, he could return for 2015's final few rounds but if he had any hiccups he could be sidelined for the rest of the regular season.

Duncan was substituted out of Geelong's loss to the Sydney Swans in the third quarter last Saturday night and spent the rest of the game on the bench with his foot elevated.

"Mitch Duncan is going to struggle to get back in the home and away season, which would be a big loss for Geelong's midfield," Larkins said. 

"The problem with these type of breaks is that a screw or some sort of internal metal fixation is required to hold the bone together.

"We've had a few players in the AFL who've missed three months with this sort of injury, and two to three months is the minimum recovery time after surgery."

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Larkins also said Nick Riewoldt would likely miss Saturday's clash against West Coast after suffering a high-grade concussion, but believed the St Kilda captain was unlikely to suffer any long-term side effects from his head clash with Crow Brodie Smith.

Riewoldt all smiles after leaving hospital

Riewoldt was taken straight to hospital after colliding heavily with Smith in the opening term of the Saints' loss to the Crows last Saturday and was not discharged until the following morning.

Larkins expected St Kilda would take a conservative approach and rest Riewoldt from Saturday's clash at Etihad Stadium.

"It was certainly a high-grade concussion, Nick was unconscious in mid-air before he hit the ground," Larkins said.

"But we know historically that just because a concussion is a high-grade one doesn't mean it takes longer to get better. Even after mild concussions, players can take weeks to recover.

"But if you look at the way clubs are treating high-grade concussions this year, the player usually misses a week. It's not mandatory for them to do so, but the process of recovery is slower and there's a whole series of tests they've got to go through."

Riewoldt also suffered whiplash – but no related concussion – in a collision with Giant Tom Bugg in round one, but Larkins did not believe the Saint's first concussion for 2015 would make him reconsider his football future.

"I'm always loathe to say there's no long-term effects with concussion, because in this era we're looking at what the long-term effects are on people who've had multiple concussions, but one high-grade concussion doesn't mean Nick is going to have long-term effects," he said.

"At this stage I think the Saints will just judge it on its merits and treat it as a single concussion that needs a full recovery." 

Similarly, Larkins said Smith would probably be sidelined from Saturday's game against Greater Western Sydney, with the  defender's recent history of concussions likely to convince Adelaide to rest him for a week.

Smith's teammate Matthew Jaensch was also stretchered from the field with a knee injury in the third quarter of the Crows' win over St Kilda.

Scans on Monday confirmed Jaensch had become the 10^th AFL player to suffer a ruptured anterior cruciate ligament this season, with Larkins saying the Crow was unlikely to return until this time next year.

Collingwood defender Alan Toovey was substituted out of the Pies' loss to Richmond in the third quarter with an injury to the knee he had reconstructed in 2013.

Larkins said Toovey had not suffered any damage to his ACL graft but was in doubt for Collingwood's clash against Gold Coast this Saturday.

"The concern would be that a relatively minor change of direction caused him to feel pain in his knee," Larkins said.

"It certainly wasn't a rupture of the ACL but once you've had an ACL injury, your knee becomes more vulnerable to other things."

North Melbourne's Ben Brown also injured a reconstructed knee in the Roos' win over Essendon on Friday night, with the forward substituted out in the third quarter after hyper-flexed the left knee he had repaired in 2010. 

"North is happy that he hasn't got a graft tear. The looseness in his knee was pre-existing and he was wearing strapping on the knee even in the pre-season because of soreness," Larkins said.

"I expect he's probably stirred up the lining of the knee and maybe even got a bit of swelling there which will limit his training during the week. 

"I think with North having to play interstate against Fremantle he's in some doubt to get up this week."

Larkins also said:

-Tom Hawkins missed Geelong's loss to the Swans with a minor glute strain but was expected to return on Friday night against Carlton despite some lingering soreness.

-North Melbourne skipper Andrew Swallow may have scans on the thumb that was badly knocked against Essendon, with the club expecting them to reveal a ligament injury rather than a minor break. He should be able to play with strapping against Fremantle on Saturday night.

-Roos defender Lachy Hansen jarred his hips a couple of times against Essendon but does not look to have suffered any new damage. Hansen had surgery on both hips in the off-season and faces an on-going management issue. If he's too sore to train this week, he's unlikely to play against the Dockers.

-Bomber forward Jake Carlisle (pinched neck) could return against the Brisbane Lions on Sunday after scans ruled out any fractures or spinal damage. Physio this week should ease the nerve pain and muscle spasm that sidelined him against North.

-First-year Bomber Kyle Langford (corked quad) is expected to miss the Lions clash after pulling up very sore at the end of the North loss.

-Ryan Griffen could miss the Giants' game against Adelaide this Saturday after twisting his knee against Carlton. The midfielder escaped ligament damage but will probably have scans to see if he suffered cartilage damage.

-Jesse Hogan missed the Demons' loss to Hawthorn with soreness in his back, glutes and hamstrings but should be fit to train this week ahead of Sunday's clash against the Western Bulldogs.

-Melbourne's Christian Salem suffered a high hamstring strain against Hawthorn and is likely to miss at least two or three matches.

-St Kilda veteran Leigh Montagna (hamstring soreness) should train and press for selection in Saturday's game against West Coast.

-Fellow Saint Jack Lonie suffered a low-grade concussion against Adelaide and is more likely to play than Riewoldt.

-Eagles defender Jeremy McGovern missed the win over Gold Coast with a small bleed in his calf and remains in doubt this week.

-Gold Coast is expecting midfielder Harley Bennell to recover from a corked knee in time to take on Collingwood on Saturday.

-Carlton midfielder Patrick Cripps is likely to play against Geelong on Friday night after he was a late withdrawal from the Giants loss with calf tightness and bleeding.