Millwall obviously considered themselves more than unlucky to miss out on last season's play-offs if the player's attitude was anything to go by in this match whereas Rotherham, happy to escape relegation last term, looked like the team that could go places.
The home side started brightly but the Millers were better organised and stuck to their gameplan throughout, playing deep and counter-attacking at pace.
The visitors deservedly opened the scoring when Paul Warne looped a 23rd minute cross into the Millwall area where he found Darren Byfield who caught his markers by surprise and outjumped them to head home.
Millwall battled back and Neil Harris brought the best out of Mike Pollitt with a curling effort from the edge of the area which was tipped over the bar.
The game was up for the Lions when Tim Cahill conceded a free kick just three minutes later. Mike McIntosh's 30-yard strike, although seemingly weak, slipped out of Tony Warner's hand and into the net to make it 2-0.
Rotherham made it three with another bizarre goal just seven minutes into the second period when a long ball was lobbed over the Lions defence, bounced off of Darren Ward's boot, onto Byfield's knee, to trickle under the hapless Warner.
Oddly, Millwall were enjoying the majority of the possession and chances, but Chris Sedgwick's opportunism made it four when he drifted past Robbie Ryan to place wide of Warner's outstreched hand.
Millwall fell apart after this and two goals in a minute completed the 6-0 thrashing.
First Alan Lee squared in the 80th minute to Darren Garner who placed a pinpoint pass into the path of Byfield who chipped over Warner for his third and Rotherham's fifth.
Byfield's fourth was a similiar move with Lee again playing a through ball for him to run straight through to score much to the obvious delight of Rotherham's 267 shellshocked supporters