And it could leave the fly-half with just one remaining opportunity to prove his fitness ahead of England's RBS 6 Nations Championship opener against Italy on February 15.
Wilkinson has played barely 50 minutes' rugby since the World Cup, which was confined to one appearance for Newcastle against Northampton three days after Christmas.
The Falcons face two blank weekends loom while the quarter-finals take place if they are knocked out. That would leave Wilkinson with only the Premiership clash at Gloucester before England kick off their RBS 6 Nations campaign.
If Newcastle eliminate Montferrand, then it is thought that Wilkinson might be considered for a place on the bench against probable quarter-final opponents Saracens on January 24 or 25.
Wilkinson is among four of England's World Cup final team injured and definitely sidelined for European action.
Matt Dawson, Richard Hill and Mike Tindall are all out - while prop Phil Vickery (rib injury) is unlikely to make Gloucester's Heineken Cup clash against Munster.
And three substitutes used during the Sydney final - Mike Catt, Iain Balshaw and Lewis Moody - are also currently out of action.