As a result of Boro's recent inconsistency, the Lions now sit just four points adrift of their 12th-placed opponents in the standings.
Match preview
There have been times this season when Middlesbrough supporters may have had second thoughts over Michael Carrick, who has come nowhere near to replicating last season's run to the Championship playoffs.
With two defeats in three second-tier fixtures over the Christmas and New Year period, Boro are no closer to achieving that goal for the second campaign in succession.
However, while Boro are sitting in 12th position in the standings, they are one game away from reaching the EFL Cup final, a consequence of beating Chelsea 1-0 in Tuesday's first leg of their semi-final tie.
Missed chances from their Premier League opponents helped matters, yet the Blues could have few complaints as Middlesbrough ground out a narrow success ahead of the reverse fixture at Stamford Bridge.
Carrick will call for focus on the league at this point, a winnable home encounter against Rotherham United to be played before the second leg, as well as Saturday's trip to Millwall.
Joe Edwards endured a shaky start in charge of the Lions, but his players have since responded by putting together a five-game undefeated streak in the league.
Consecutive victories have been posted over Queens Park Rangers, Norwich City and Bristol City, with clean sheets being kept in the process.
Now 10 points clear of the relegation zone, Millwall can target compiling a promotion bid, the gap to fifth-placed West Bromwich Albion standing the same as the margin to the bottom three.
Millwall did suffer disappointment last weekend, though, as they succumbed to a 3-2 reverse at the hands of Championship leaders Leicester City in the FA Cup.
Millwall Championship form:
L
D
D
W
W
W
Millwall form (all competitions):
D
D
W
W
W
L
Middlesbrough Championship form:
L
W
W
L
W
L
Middlesbrough form (all competitions):
W
L
W
L
L
W
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Team News
With Ryan Leonard expected to miss out through injury, Wes Harding could be selected in the Millwall back three in his place.
Edwards also has the option of recalling Joe Bryan at left wing-back and moving Murray Wallace into a central-defensive role.
George Saville remains suspended, though, while Tom Bradshaw should get the nod over Kevin Nisbet in attack.
Alex Bangura and Emmanuel Latte Lath have joined Middlesbrough's extensive injury list after sustaining issues against Chelsea.
Carrick must decide whether to switch to a back four, but Matt Clarke and Josh Coburn could be in line to play in the roles that they excelled in on Tuesday.
Sam Greenwood and Morgan Rogers return to the fold after they missed the Chelsea game through being cup-tied and suspended respectively.
Millwall possible starting lineup:
Sarkic; Harding, Hutchinson, Cooper; Norton-Cuffy, Honeyman, Mitchell, Wallace; Watmore, Flemming; Bradshaw
Middlesbrough possible starting lineup:
Glover; Van den Berg, Fry, Clarke; Jones, Barlaser, Howson, Engel; Rogers, Hackney, Coburn
We say: Millwall 1-1 Middlesbrough
The high of beating Chelsea could have varying effects on Boro, something that Carrick will be aware of. Millwall are a team in form right now, and that may lead to the two teams playing out a competitive draw at The Den.