BILLY Driscoll is racing against time to be fit for North Ballarat's next assignment - a Victorian Football League preliminary final next Saturday.Driscoll is doing everything asked of him to recover from a cracked heel.However, he will face his biggest test at training on Wednesday.He must get through that session at full pace to have any chance of selection for the knockout match against the winner of today's semi-final between Williamstown and Collingwood.The Selkirk Roosters' leading goalkicker this year, Driscoll has not played since August 8. He has missed four matches, including North Ballarat's 48-point win over Port Melbourne in a qualifying final a week ago.Head coach Gerard FitzGerald said while Driscoll's attitude to recovery had been impeccable, he faced a challenge to be fit for the preliminary final."Time is his enemy. We won't be rushing him."He's been doing light training and is on schedule."FitzGerald said his next challenge was to see how he stood up to putting weight on the heel at full pace.He said Driscoll had to go through the same process that Dan Feery (lower leg) and Shaune Moloney (calf) had last week.Feery defied the odds and was one of the Roosters' best in two run-with roles against Port Melbourne.FitzGerald said earning a weekend off on the way to a preliminary final had been most beneficial for his players.He said it had enabled everyone to freshen up mentally as well as physically.North Ballarat had its main training session for the week last night, with its North Melbourne-listed players joining in.FitzGerald and his coaching panel will attend the Williamstown and Collingwood clash today, but not the players.They will watch the Roosters' reserves in a preliminary final at Port Melbourne tomorrow.VFL DRAWSENIORSSEMI-FINALS at Port Melbourne, 1.10pmTODAY: Williamstown v Collingwood TOMORROW: Port Melbourne v Box Hill Hawks RESERVES PRELIMINARY FINALS, 10.20amTODAY: Williamstown vs Sandringham TOMORROW: Box Hill Hawks v North Ballarat