Alex Lawless and John Hardiker are facing a race to be fit for the biggest game in Forest Green's history.
Rovers boss Jim Harvey has confirmed that midfielder Lawless, who missed Saturday's sensational FA Cup second round defeat of Rochdale, is likely to be absent for around a month due to a back problem.
Longer-term absentee Hardiker requires another four weeks' treatment at least on his injured knee, so is extremely unlikely to be available when Championship giants Derby County roll up at the New Lawn for a sell-out third round tie on January 3 or 4.
Harvey said: "The biomechanics in Alex's back are out of sync, so he's going to need some orthotics (insoles), which take a fortnight to come. John is also a long way off. Both boys are desperate to get back, but I'm afraid there is no quick fix for either of them."
The unfortunate Hardiker has now been replaced as permanent club captain by Lee Fowler, a reflection of how quickly the close-season signing from Newport County has become an authority figure.
"Lee was a potential captain in the summer, but he was a new arrival at the club and I didn't know enough about him to give him the job," said Harvey. "But he has come to the fore as the season has gone on and has all the qualities required."
Harvey is also thrilled to have secured the services of on-loan Wrexham defender Darran Kempson for a further month, including the clash with the Rams.
"Darran came in when both John Hardiker and Mark Preece were out and we were really struggling," he said. "He has made a massive difference, as has (player-coach) Jerry Gill with all his experience at right- back."
Forest Green have confirmed that the Derby tie will be all-ticket, with full details due to be released after a meeting between the two clubs and respective police forces on Thursday.
Rovers secretary Colin Peake said: "Our supporters will be aware of the priority for securing tickets, and these will be re-iterated when the final arrangements have been made.
"There is no requirement to send any communication to the club at this stage with any form of payment in any attempt to secure tickets before they are available."
Anyone interested in hospitality suites, sponsorship and other matchday packages should contact the commercial and marketing department on 01453 834860, or e-mail email@example.com.
Rovers return to action tonight with a home tie against Torquay United in the Setanta Shield fourth round (kick-off 7.45pm).
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