There were plenty of individual performances to admire as Albion kept alive their hopes of Championship survival with a heartening victory.
Paul Reid celebrated his recall with a swift and crucial breakthrough.
Paul McShane, the other early goalscorer, was inspirational once more and Adam Hinshelwood alongside him at the heart of the defence is getting better with every game following his long injury lay-off.
Gifton Noel-Williams, giving the Seagulls a new lease of life, brought the best out of Colin Kazim-Richards, who persistently troubled Millwall's pedestrian trio of centre backs.
But there could be only one man-of-the-match on this occasion - even though he was not playing.
Manager Mark McGhee plotted his old club's downfall with a grand plan which paid off to perfection.
The Albion fans prone to criticising McGhee's tactics must have thought it was an April Fool's trick when they heard Guy Butters' name missing from the starting line-up for the first time this season.
It was a big call to leave out the dependable, if ageing, skipper for such a big match.
Even bigger when you consider, without Butters' experience, McGhee relied on surely one of the youngest back fours in the club's history, with Adam El-Abd and Joel Lynch either side of McShane and Hinshelwood.
That's not all. McGhee also decided to begin with to use Gary Hart as a third striker alongside Albion's double-barrelled duo.
The reasons for the changes were two-fold. Butters' omission allowed the defence to squeeze up and the young fullbacks in particular to nullify the influence of the Millwall wingbacks, Alan Dunne and Jamie Vincent.
At the other end of the pitch, McGhee was banking on his three-pronged strike force catching the hosts by surprise and muffling the Lions' roar following their surprise victory at Watford the week before.
It was bold, perhaps desperate to a degree given the four-point gap between the sides and the nine-point chasm between Albion and safety at kick-off but golly did it work.
In fact, it worked even better than McGhee dared to imagine. The match was won and lost in the opening 11 minutes, as the Seagulls sprinted into a two-goal lead.
Reid, excluded from the starting line-up since the home defeat by Leicester in mid-February, pressed his case for a return with two goals from midfield for Dean White's Reserves a week ago.
White's advice to McGhee that "Reidy has got a goal in him" rang true after only six minutes.
The Antipodean, operating on the right of a three-man midfield, calmly tucked away his second of the season after Millwall keeper Andy Marshall, hampered by Hart making a nuisance of himself, failed to hold a high, hanging cross from Noel-Williams.
Millwall were still in shock when, five minutes later, Albion had the comfort of a two-goal lead not enjoyed since the high-scoring draw at Leeds in early September.
McShane, responsible for the only previous away victory (as if anyone could forget) at Crystal Palace in October, met a corner from captain for the day Richard Carpenter to head his fourth of the campaign.
You had to feel some sympathy for Dave Tuttle, a Millwall player under McGhee. The customary hangdog expression of the Lions' chief multiplied as he was completely out-manoeuvred by his master.
By the time Tuttle, cruelly berated by some of the vociferous home fans, woke up to the disaster unfolding before his eyes, it was half-time.
Ben May, Millwall's young leading marksman, and lively left winger Marvin Williams were simultaneously brought on.
McGhee's response, the introduction of Kerry Mayo and a return to 4-4-2, had the desired effect. The hosts huffed and puffed while, on the break, Albion could and should have added to their tally.
McGhee, reflecting on his tactics, revealed: "I said to the lads if we did it right we could be ahead before they even realise what is happening.
"The first goal took the wind right out of their sails and it was a dream to get two.
"It was a massive ask for us to win this game and I think it reflects a wee bit again the arrival of Gifton.
"Had we had Gifton two months ago I don't know that we would be in this position, because he has made a difference."
Momentum is building on the back of a four-match unbeaten run. Suddenly Albion have gone from no-hopers in the survival stakes to the kind of live outsider punters will be latching onto in Saturday's Grand National.
McGhee said: "The belief will return, not only that we can win. It will also register that Gifton is here and has made a difference.
"With Southampton coming up at home, it gives everyone the belief it's not impossible.
"It won't be a miracle. It's going to be a helluva lot of determination and hard work from the boys and retaining that self-belief in each other but it's possible."
McGhee might have been describing Hart in that sentence. The bloody-mouthed utility player's contribution on Saturday was restricted to 37 minutes by an alleged elbow from Matt Lawrence.
McGhee and his players are entitled to grin today, even if Hart cannot. It is Millwall who have just suffered the most important kick in the teeth.
- Albion (4-3-3): Henderson 7; El-Abd 7, McShane 8, Hinshelwood 8, Lynch 7; Reid 8, Carpenter 7, Hammond 7; Kazim-Richards 8, Noel-Williams 7, Hart 6. Subs: Gatting 5 for Hart (injured 37), Mayo 6 for Gatting (withdrawn 51), Butters for Noel-Williams (withdrawn 88), Dodd, Chaigneau.
- Millwall (3-5-2): Marshall; Robinson, Lawrence, Whitbread; Dunne, Elliott, Cameron, Livermore, Vincent; Hayles, Asaba. Subs: May for Vincent (withdrawn 46), Williams for Asaba (withdrawn 46), Braniff for May (injured 87), Doyle, Craig.
- Matchfacts
- - Shots on goal: Albion 5 Millwall 2.
- Shots off goal: Albion 6 Millwall 8.
- Corners: Albion 5 Millwall 5.
- Off-side: Albion 6 Millwall 6.
- Free-kicks: Albion 15 Millwall 14.
- Albion bookings: None.
- Millwall bookings: Robinson (40) foul, Cameron (69) foul, Hayles (85) dissent.
- Albion scorers: Reid (6) McShane (11).
- Millwall scorer: None.
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