Derby duo Paul Green and Gareth Roberts could miss the remainder of the season after suffering knee injuries against Cardiff.
Both players left the field on a stretcher during the 4-1 defeat in south Wales on Saturday.
Green appeared to fall awkwardly just before half-time, and the fear is the midfielder could be facing a long lay-off. Left-back Roberts was carried off after an hour after laying injured during the build up to Cardiff's third goal.
The pair are set to undergo scans to discover the extent of the damage.
"We suspect it is knee ligament damage for both of them," said manager Nigel Clough.
"If that is the case and our fears are confirmed, they will be out for the rest of the season and both could be looking at quite a spell on the sidelines."
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