NORTH Melbourne will probably have to win five or six of its remaining games to reach the finals for the second consecutive year, according to coach Dean Laidley.

In a year where the Roos have been hit by injuries to key players and found it difficult to maintain good form, particularly on the road, Laidley said a finals berth would be a "wonderful achievement" for the young players who have filled the breech this season.

Laidley believes the Roos will need to win at least five, possibly six of their remaining games to make the finals. "The more you win, you give yourself a bit of breathing space, but when it becomes four out-of-four or three out-of-three it becomes quite difficult and the games take on a whole new realm of importance but, the reality is, they're all important games," he said.

The Roos start their assault with tonight's match against Collingwood at Telstra Dome and face a difficult challenge having to also play the Brisbane Lions at Carrara, the Bulldogs and Geelong all before September.

But while the Roos have been inconsistent this year, their best results have come against the competition's best teams.

"I'm pretty confident of our playing group every time we've played in Melbourne on the big stage against any opposition," he said.

"We've beaten Collingwood earlier this season in a very, very, tight game. (Against) Geelong we played very well, we've beaten the Bulldogs, we drew with Sydney, we've beaten the Hawks, so our form in Melbourne has been pretty good against anyone."

The Kangaroos have ruled out talented defender Jesse Smith for the rest of the year with hamstring problems, which plagued the 21-year-old all year and caused him to lose confidence.

For the highly rated son of former North defender and current Hawthorn assistant Ross Smith, this is the second season injuries have ruined. He has played just two games this year and missed all of 2006 because of an ankle injury. Last year, he managed 19 games including the Roos' finals campaign.

Laidley said Smith was struggling with the latest injury blow after an interrupted pre-season.

"He's struggling with the mental side of it, he really is," Laidley said.

While the ankle is no longer the problem, Smith will start a program based on strengthening his legs and running, effectively starting his pre-season now before taking a break with the rest of the group over summer.

"He just hasn't had the strength in his legs and his lack of conditioning from not training and coming off a limited pre-season means the confidence in his legs is just shot at the moment. We've jumped from one problem to the next."

The Roos could regain Jess Sinclair and Andrew Swallow soon. Sinclair has missed most of the year because of thumb and ankle injuries, and Swallow broke a bone in his foot, but Laidley suggested the pair could be back in a fortnight.