Joel Tippett is set to miss up to six weeks after copping a knee to the back in a VFL practice match.
Tippett suffered extensive bruising to his lower back and a fracture of the transverse process, a small bony projection off the side of his vertebrae, while playing for Werribee against Footscray.
"Joel reported immediate pain and spasms in his lower back," North director of football Geoff Walsh said.
"Things have now settled and he will have follow up scans as part of his treatment."