However the situation has now become so bad that an operation is essential, ruling the 34-year-out for around five weeks.
"Macca's injury has progressed to the point where it's restricting him. He can't continue and he has to get something sorted out," Groves told the Grimsby Telegraph's Matchday supplement.
"He's due to see a specialist today. It's generally a five-week span where you're out and we're looking at March.
"It's a blow and we don't want to lose anyone with his experience and the level of performance that he gives us.
"He'll have the surgery as soon as possible if, or when, it's confirmed that that is the problem."
Utility man Jason Crowe will cover at rightback in McDermott's absence with both Iain Ward and Wes Parker both on the injured list too.