Darren Crocker's hopes of lifting North Melbourne out of the doldrums during his spell as caretaker coach have received a setback with star on-baller Daniel Wells again breaking down at training.

Wells has played just seven games this season and has not played since Round 11 due to groin problems.

But Crocker, who will have his second match in charge following the shock resignation of Dean Laidley when the Roos travel to Sydney on Sunday, said on Thursday that Wells was set to spend several more weeks on the sidelines.

"He is still having a few issues with those groins and we just want to make sure when we bring Daniel back he is 100 percent ready to go," Crocker said.

Crocker said Wells suffered a setback at training ahead of last week's match against the Western Bulldogs, where North performed gallantly in Crocker's first game in only going down to the third-placed Dogs by four goals.

"He did the main training session last week because he was keen to play but towards the end of training he got a bit sore and began to tighten up," Crocker said.

"He just didn't have the zip that was required and I had a good chat to him and I just said 'I really want you to be 100 percent when you come back rather than have you play two or three games and then we are in the same situation again'."

Crocker admits it is a frustrating situation for Wells, the Roos' 2006 best and fairest runner-up and pick two in the 2002 national draft who is seen to have never lived up to his early potential but remains one of the club's most important players.

"Daniel Wells at the top of his game would give everyone an enormous boost," Crocker said.

"But we don't want to bring him back into a situation where he puts himself under enormous pressure."

Crocker said Wells' condition was being closely monitored but could not be cured by surgery.

"It's not a surgical thing it's a debilitating groin issue and we are trying to manage him through it and if we can get him back in the back half of the year that would be great."

"We got a big lift last week with getting 'Boomer' (Harvey) back (from injury) because he just adds that leg speed and class and Daniel Wells and Matty Campbell (who remains sidelined with a hamstring strain) are the same and the sooner we get then all back, the sooner we will be a better side."