With just 12 wins and 52 points in the bag so far, the Lions are languishing in 10th position in the table.
Despite having a relatively solid defense, they struggled with inconsistencies all season, with a misfiring frontline a cause for concern.
Jed Wallace is the side's top-scorer with seven goals, while no other player in the squad has accrued more than five.
Having guided them to an eighth-place finish last year, Gary Rowett must pull a rabbit out of his hat if he is to take them further up in this campaign.
Rotherham are in a more dire situation and are staring at the possibility of going back down into League One, having only gained promotion last summer.
With just 10 wins and 35 points accrued so far, the Millers are 22nd in the league standings. However, they have four games in hand over Birmingham City above them.
Millwall vs Rotherham United Head-To-Head
In 37 meetings between the sides, the spoils are closely shared, with Millwall winning on 13 occasions and Rotherham victorious 14 times.
In the first leg of their clash this season, the Lions registered a 1-0 win in Rotherham.
Millwall Form Guide (all competitions): W-L-W-L-W
Rotherham United Form Guide (all competitions): L-L-W-L-W
Millwall vs Rotherham United Team News
The home side will continue to be without Maikel Kieftenbeld as the midfielder is currently recovering from a knock.
No player is currently suspended from the clash, but the likes of George Evans and Mahlon Romeo are one booking away from a ban.
Injured: Maikel Kieftenbeld
The Millers have a clean bill of health going into the match. The injured trio of Jamie Lindsay, Chiedozie Ogbene and Clark Robertson are back in the mix and available for selection.
Ben Wiles, who picked up a hamstring injury in the defeat to Watford two weeks ago, was on the bench in the Bristol game. He may return to the starting XI here.
Millwall vs Rotherham United Predicted XI
Millwall (3-5-2): Bartosz Bialkowski; Shaun Hutchinson, Jake Cooper, Murray Wallace; Danny McNamara, George Evans, Billy Mitchell, Ryan Woods, Scott Malone; Mason Bennett, Jed Wallace.
Rotherham United (3-5-2): Viktor Johansson; Richard Wood, Angus MacDonald, Michael Ihiekwe; Matthew Olosunde, Dan Barlaser, Shaun MacDonald, Ben Wiles, Wes Harding; Matt Crooks, Freddie Ladapo.
Millwall vs Rotherham United Prediction
Millwall may seem the obvious favorites here but Rotherham are looking to make the most of the games they have in hand.
It'll be tough for them but we expect a pulsating encounter at The Den with the spoils being shared once again.
Prediction: Milwall 2-2 Rotherham United