Revell is the Millers top scorer so far this season with 4 goals, however its looking that he will be joining the Bluebirds possibly before this weekends games.
Cardiff boss Russell Slade is keen to bolster his attacking options and knows Revell well, having managed him at Brighton and Leyton Orient, while also being on the Wembley touchline as the Millers man scored two goals in last season's League One play-off final against his O's side.
Revell, joined the Millers in 2011, has been a favourite of manager Steve Evans but, despite his success for the club, has come under fire from a section of fans unhappy at his lack of goals.
The striker, who has scored 34 times in 170 appearances, is out of contract in the summer and it is believed talks over a new deal have gone quiet. He sat out the 5-1 drubbing against Bournemouth in the cup last Saturday, with a chest infection the cause, the first time in 121 games he has not been included in the matchday squad, going back to October 2012.
Preston, Barnsley and Sheffield United have also been linked with a move for him