The 29-year-old former Cambridge centre-forward who is out of contract at the end of the season, will become a Rotherham player if he can agree personal terms with the Millers as Reading agreed a £150,000 fee with the South Yorkshire side for the forward's services.
Rotherham are keen to take another striker to Millmoor having sold top Republic of Ireland international forward Alan Lee to Cardiff for £850,000, leaving a massive whole in their team which they believe Butler can plug.
Ronnie Moore has made his dramatic transfer swoop just three days after his side were at the Madejski Stadium to face the Royals. Ironically, Butler came on as a late substitute, playing against the side he may soon call his own.
Reading's decision to let Butts leaves seems somewhat peculiar given his two recent first team appearances and a five goal reserve team haul last week. What's more, the Royals will find themselves short of strikers should Mr Butler decide to pack his bags.
Whilst Shaun Goater and Nicky Forster are the first choice front two right now, should Butler depart Pardew would have to look at bringing someone else in as the only reserve players available are the somewhat raw Bas Savage and Darius Henderson (who is out on loan at Brighton).
Martin Butler joined Reading for a club record £850,000 fee in February 2000 from Cambridge United. The 5ft 11 inch man has since gone on to notch up 117 appearances for the Royals, he has scored 30 times. However, since sustaining a serious injury two years ago, Butts has hardly featured in the first team.