DEFENDER Matt Sharkey failed a fitness test last night and will miss North Ballarat's encounter with Collingwood in the Victorian Football League at Eureka Stadium in Ballarat tomorrow.Sharkey is out with an injured right wrist.Last year's joint best and fairest had difficulty at training on Wednesday and was pencilled into the line-up pending getting through last night's session on the new surface at Eureka Stadium.Sharkey passed an initial tackling exercise before complaining about soreness.Sharkey is one of four changes.North Melbourne quartet Aaron Edwards, Ed Lower, Gavin Urquhart and Sam Power are inclusions along with North Ballarat Rebels player Josh Free, who will play under AFL Victoria's 23rd man rule. This allows a TAC Cup player to be used as an extra man.As well as Sharkey, Liam Anthony, Paul McMahon and Nick Peters are out of the team which overcame Frankston two weeks ago, the last time the Selkirk Roosters played.Anthony makes his debut with North Melbourne against the Western Bulldogs tomorrow, while McMahon and Peters have been unable to retain their place in the team.This will be Power's first game with North Ballarat.Lower and Edwards have played just the one VFL game this year, while this will be Urquhart's first appearance for North Ballarat since last year's grand final victory. One of head coach Gerard FitzGerald's biggest challenges tomorrow will be ensuring the five newcomers blend into what is a tightly knit winning combination.Keeping the bulk of his defence will make this job easier.Although Sharkey will be missed, a constant rotation through the backline this season means Shaune Moloney, Marc Greig, Shannon Watt, Brett Goodes, Dan Feery and Michael Searl are a well-oiled machine and will be ready for whatever a well credentialled Collingwood attack has in store for it.Moloney rarely gets an easy day out, and running into Anthony Rocca will be no exception, but he has been up to every challenge so far, and this is one he will relish.Keeping Paul Medhurst quiet will be another major aim.There was a train of thought this week that Collingwood would recall him to AFL ranks, but this did not happen.The excellent form of Brad Dick and Alan Didak saw to that."He's been back training and training well, but he's not going to replace Dick and he's not replacing Didak," Collingwood coach Mick Malthouse said yesterday.This is sure to fire up Medhurst.North Ballarat is going to find something extra though, being at home for the first time this season.The Roosters have been eager to get onto the new-look ground and midfield running powers Steve Clifton, Myles Sewell, Tom Roach and Cam Richardson will love the spacious surrounds, as will the big marking brigade of Orren Stephenson, Tristan Cartledge, Michael Wundke and Josh Smith, who should be able to find space easier.On the day the Roosters unfurl their first VFL premiership flag, they will want to mark it with with a victory.