Derby midfielder Stephen Pearson faces at least a month on the sidelines after suffering a slight groin muscle tear.
The Scotland international had featured in all nine of the league and cup games this season before sitting out Saturday`s home Championship victory over Bristol City.
Pearson injured his groin in training at the end of last week and scans have revealed the 26-year-old has a tear.
Boss Nigel Clough said: "It looks like Stephen will be out for four weeks."
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