Former Sheffield Wednesday chief Stuart Gray is the bookmakers' favourite to succeed Steve Evans at the AESSEAL New York Stadium.
Evans left the Millers this afternoon after a meeting with chairman Tony Stewart, a club statement later revealing that Evans and Stewart wished to "go in different directions".
And Gray, who was relieved of his duties at Hillsborough in the summer following Dejphon Chansiri's takeover of the Owls, is currently 7/4 favourite, with league sponsor SkyBet, to take the reigns at Rotherham.
Neil Redfearn, formerly of Leeds United, is keen to speak to the Millers, according to Press Association, and is currently 7/2 with Ian Holloway (8/1) third favourite.
A host of former local managers are considered in the running; including former Reds chief Keith Hill and ex-Owls hero John Sheridan (both 12/1), two more former Hillsborough men Alan Irvine and John Pearson (16/1) and former Sheffield United bosses Neil Warnock (12/1) and Nigel Clough (25/1).
Evans, whose side beat Birmingham at the weekend to move out of the Championship drop-zone, delivered two promotions for the Millers and kept them in the second tier last season.
A club statement, confirming the departure of Evans and assistant Paul Raynor, said: "It has all come as a surprise but Rotherham United must move forward and the search for a new first team manager will begin immediately.
"Replacing Steve Evans and Paul Raynor will indeed be a strenuous task for the board.
"Rotherham United Football Club will always welcome Steve and Paul whether as an opposition management team or as supporters of our fantastic football club."