NORTH Melbourne's Daniel Wells is now facing the additional challenge of conditioning as he fights to overcome a groin injury that has hampered him for most of 2009.

Wells has not played since round 11 – or strung together more than three games this year – and in the second half of that clash with St Kilda was limited in his movement.

Chief of football Donald McDonald said the midfielder needed to get through a training session pain-free to return for Sunday's clash with the Sydney Swans.

"It's just going to depend on how he feels every week," McDonald told kangaroos.com.au.

"It's one of those injuries with abdominal muscles where there's something there and we've got to keep working to get him right.

"The longer he has out, the greater the risk of him not coming straight back into the senior team. If he has another week or two out, he's going to need some really good top-end efforts at training to ensure his conditioning is back to a required standard.

"At the minute, he's probably dropping off a little bit because he's missing so much."

Wells was also struck with a virus early last week and McDonald said five or six players battled illness as the week unfolded.

Forward Lindsay Thomas was replaced in the Roos' final side to play the Bulldogs while defender Shannon Watt sat out North Ballarat's win over Collingwood.

"A few of them took it into the game [against the Dogs] and got through, so it was a little bit alarming at the end of last week but hopefully we've seen the back of it," McDonald said.

After spending the bulk of the last 18 months battling hamstring and ankle injuries, highly-rated half-back Jesse Smith is ready to return through the VFL.

However, he will have to wait one more week because of North Ballarat's bye and so will forward Matt Campbell (hamstring), who McDonald said was no chance of a call-up to play the Swans.

McDonald added that he had visited youngster Ben Warren in hospital since the 20-year-old broke his leg early in Sunday's loss to the Dogs.

Warren was in his first game back from a fractured cheekbone that had sidelined him for two weeks, including the mid-season bye.

Despite his latest injury and the likelihood his season was over, McDonald said Warren's spirits were good.

"He's an effervescent sort of a character so he'll be alright," he said.

"We're really disappointed not to have him. We've just got to cop it on the chin and keep moving."

McDonald said key position player Robbie Tarrant would have his left shoulder reconstructed on Wednesday.

Rookie-listed defender Luke Delaney had the same surgery on Saturday.