While the Lions are one win away from potentially breaking into the top six, Blackburn can move ahead of their hosts with victory in East London.
Despite having recorded four points from their last two matches, Blackburn's run of three successive defeats immediately before that improvement looks likely proving to be decisive.
Although Rovers only sit four points adrift of the playoffs, six teams stand in their way, realistically too many with just three games remaining on their schedule.
Nevertheless, Tony Mowbray will have set his side the target of registering three successive victories against Millwall, Reading and Luton Town to keep the pressure on the clubs above them.
Having collected four points from promotion-chasing Cardiff City and West Bromwich Albion, Mowbray will feel that his players are heading in the right direction, particularly in attack with five goals coming from their last three outings.
Adam Armstrong has netted two of those strikes, taking his contribution to 14 goals and six assists for the campaign.
Like the visitors, a three-match winless streak has left Millwall as outsiders for the top six, but Gary Rowett will be delighted with his side after six points were recorded from their last three matches.
While succumbing at home to Middlesbrough was an obvious disappointment, narrow wins at Charlton Athletic and Hull City would have answered questions about his team's character.
With just two points the gap to the playoffs, as well as Queens Park Rangers and Huddersfield Town being their final two opponents, Rowett will feel that three more wins will be enough to nip in ahead of several teams over the course of the next 10 days.
Rowett's one major concern will be regarding his attack, with just three goals being scored in their last five fixtures.
Millwall Championship form: LWWDLW
Blackburn Rovers Championship form: WLLLWD
Having witnessed his side's resilient performance at Hull, Rowett is likely to keep the same starting lineup.
Mowbray is likely to assess the fitness of Blackburn left-back Joe Rankin-Costello, who came through 90 minutes against West Brom despite initially being regarded as a fitness doubt.
Millwall possible starting lineup:
Bialkowski; Hutchinson, Pearce, Cooper; Mitchell, Woods, Leonard, Ferguson; J.Wallace, Bennett; Bradshaw
Blackburn Rovers possible starting lineup:
Walton; Nyambe, Lenihan, Adarabioyo, Rankin-Costello; Travis, Downing, Rothwell; Samuel, Graham, Armstrong
We say: Millwall 1-1 Blackburn Rovers
With everything at stake, the general consensus is that both teams will go all out for victory. However, they will also be wary of conceding the first goal, and we feel that mindset will lead to a low-scoring draw being played out.