Luke McDonald is expected to miss several weeks of football after injuring his hamstring on Friday night.
The defender injured the tendon while chasing down Hawthorn's Cyril Rioli at Etihad Stadium and will require surgery.
"It was a tremendous effort for Luke to lay the tackle and save what would have been a goal," Director of Football Geoff Walsh told NMFC.com.au.
"Luke has had a great year and his loss will be felt, but it gives one of our other defenders a chance to come into the side and fulfil a role for us in the second half of the year."
The club will communicate a more specific length of rehabilitation for McDonald after the procedure is performed.
Lachlan Hansen could be named to take on the Crows on Thursday after being rested in the second half of Werribee's game against Essendon on Saturday.
Daniel Wells remains doubtful for the club's next clash in Adelaide while Taylor Garner suffered another hamstring setback at training and could miss 3-4 weeks.
For more NMFC injury news and the full injury list, visit the Anytime Fitness Health Hub