Forced into an interval just before the break by Marcus Tavernier's injury, the Middlesbrough manager, who these week raised smiles by comparing himself to a Coronation Street character, used three more substitutes at the break. Warnock is nothing if no pro-active.
The trouble was, plan B did not work either – at least not well enough to overturn the one-goal lead Grant Hall's own goal had given the hosts before the rethink. Millwall just got players behind the ball in the second half and made life tough for their opponents.
Neither of this sides fuss too much about putting on a spectacle for the fans, so when there are none in, the focus is all on getting the job done. Millwall did and for all their second-half huffing and puffing, Boro missed the chance to take advantage of slip-ups elsewhere. The Championship play-offs are starting to drift out of view.
They created a lot of their own problems in the first half, with a bit of a helping hand from Jed Wallace.
The Millwall player was given a free role in their 3-5-1-1 formation and he had the intelligence and skill top exploits the faults in Boro's shape. Warnock matched Millwall's three at the back, but beyond that it was all a bit odd.
Djed Spence, holding midfielder Jonny Howson and Marvin Johnson formed the next line, and Marcus Tavernier was in the hole behind Yannick Bolasie and Chuba Akpom. The left Paddy McNair buzzing up and down the inside-left channel between Howson and Tavernier.
But with no equivalent on the right, it left a nice hole Wallace regular shifted himself into until late in the half McNair was pulled deeper and Howson allowed to shuffle across to close it up. That and the ball in behind left-sided central defender Bola were the weaknesses he exploited and by the time Boro changed things around, Wallace had already helped his side take the lead.
The first quarter of an hour were fairly tepid, presumably because Wallace was still sizing his opponents up, releasing Mason Bennett down the right with a seventh-minute pass but he shot at Marcus Bettinelli.
Maybe getting bored, Bettinelli gave himself something to do on the quarter-hour by picking Billy Mitchell out with a pass but the central midfielder's shot allowed him to get back and block.
Wallace earned Bola a booking, pulled down on the halfway line when the defender was caught napping on the ball. Luckily for him there was a lot of grass between them and the goal and two centre-backs in the vicinity, keeping the damaged to a yellow card.
Bettinelli then had to make a very good save diving low to his left as Wallace ran onto Bennett's pass. Three minutes later, Millwall had scored, Spence giving the ball over the Mitchell, and Wallace accelerating past Howson, then drilling a cross which went in off Hall.
They should have had another 10 minutes later but in playing George Evans in behind Bola, Wallace perhaps also gave him too much time to think about the enormity of the goal he had the chance to score, and the chance was pulled wide of the far post.
All Boro could offer in return was a chance a minute later, Johnson getting to the byline and pulling back an inviting ball but the close attentions of Mitchell hampered Bolasie's attempts to get a clean contact, or to find the target for that matter.
A new front two came on at the break, and with Nathaniel Mendez-Laing on at right-wing back, the wide players were pushed high and wide in a 3-5-2. That and just maybe some dressing-room home truths at half-time saw a much improved second half... but no goal.
George Saville chested down and shot at Bartosz Bialkowski, then did so again after swivelling on a Mendez-Laing pass, and all Boro could make of an excellent Johnson ball was a deflected Duncan Watmore shot. Bola and McNair forced saves in the final 20 minutes but already you felt it was just not coming for the visitors.
Even the unused substitutes played their part, sent out to warm up by Warnock so they could play ballboys, which Sam Morsy dutifully did as Millwall did their professional best to run down the clock. When fourth official Declan Bourne lifted his electronic board up to say a minimum of three minutes would be added, he had Warnock chasing after him, livid, and more interested in chuntering about it, seemingly, than watching the rest of the game.
In truth, he did not miss much. It was not a great day for a Boro side running out of legs in the promotion race.
Millwall: Bialkowski; McNamara (Romeo 86), Hutchinson, M Wallace, Cooper, Malone (Pearce 86); Evans, Woods (Williams 80), Mitchell; J Wallace (Bradshaw 80), Bennett (Bodvarsson 64).
Unused substitutes: Fielding, Ferguson, Mahoney, Burey.
Middlesbrough: Bettinelli; Fry, Hall, Bola; Spence (Mendez-Laing 46), Howson, Johnson; McNair (Kebano 80), Tavernier (Saville 45); Bolasie (Watmore 46), Akpom (Fletcher 46).
Unused substitutes: Morsy, Archer, Fisher, Coburn.
Referee: J Linington (Isle of Wight).
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