A 2-1 reverse at Barnsley coupled with West Brom's win at Swansea leaves the gap between the two clubs at 8 points with 9 games remaining in the Championship season.
Forest again gave themselves too much to do on the road, falling behind to a Daniel Bogdanovic double at Oakwell.
Dexter Blackstock gave the Reds hope but as at Preston on Saturday there was no equaliser and no points for Billy Davies and his side.