The former Derby striker has been struggling with a tight hamstring and was sent to have a scan as a precaution but the x-ray proved to be a tear.
It's another blow for Paul Sturrock who is already without Barry Corr, Drew Talbot and Marcus Tudgay for the start of the season.
But it could have been worse for the Wednesday manager - Steve MacLean missed training today after having to have dental surgery although he should be fine for Saturday's season opener at Preston.
MacLean is now the club's only senior striker and is set to lead the line alone at Deepdale with Kenny Lunt or Chris Brunt playing just behind him.
The club also promise signing a new goalkeeper today - although it will not be Liverpool's Scott Carson.