There were two moments of January magic on a stodgy afternoon here. The first was a beguiling goal on the hour mark from Muhamed Besic, the second a fine spanked effort from Ollie Norwood to decide this fourth round FA Cup tie in Sheffield United’s favour.

In between Millwall and their Premier League visitors played out a bitty, distracted game, enlivened by Sheffield United’s best periods when a much-changed team briefly found its overlapping rhythms. Millwall were energetic in midfield but blunt in attack. By the end of a slow-burn afternoon a 2-0 victory reflected their sense of arms-length control.

The Den is a rattly, misty kind of place on days like these, the peaks of the Docklands financial district gleaming over the lip of the Dockers Stand, trains creaking by in the corners, industrial Bermondsey peeking in at the sides of those corrugated blue stands.

Millwall have been a shark-like presence for Premier League teams in recent January cup rounds. The defeat of the champions Leicester here in 2017 was notable for the noise, an atmosphere so hostile Ben Chilwell was moved afterwards to deny the (fanciful but fun) suggestion he had been too scared to go and take throw-ins.

On Saturday, the Den was only a mildly boisterous place at kick-off. With good reason perhaps. Millwall have been on a fine run under Gary Rowett. They travel to Leeds on Tuesday with a play-off spot still in their sights. Sheffield United are also preoccupied on other fronts. Progress in the Premier League has been mercurial, but they still came here having scored four times in their last six games. Time for a steady hand.

Five changes on both sides added up to an angsty opening hour of this cup tie, played out on a patchy January pitch. Billy Sharp retained his place in attack and produced a performance full of intelligent running. Millwall left out their best attacker Jed Wallace and their most mobile striker Tom Bradshaw.

Aiden O’Brien had an early sight of goal drifting in from his No 10 position, but side-footed weakly at Dean Henderson. Sheffield United looked to pull the game to the flanks in their 3-4-3 formation, with Besic a sprightly presence on the right.

It was from that side the best chance of the first half came. Chris Basham, on the overlap, nudged a neat through pass on to Sharp’s diagonal run. He took the ball wide around Bartosz Bialkowski, but his shot was cleared off the line by the prescient James Brown.

Otherwise the game congealed quietly. Millwall were busy, Jayson Molumby an artful presence in central midfield. Up front the largely immobile Matt Smith roamed hopefully, more diplodocus than raptor. As half-time approached Phil Jagielka headed over right in front of goal from a left wing corner and raged at the referee, Anthony Taylor, about some perceived shirt-holding, much to the amusement of the Cold Blow Lane end. No VAR here.

The second half picked up where the first had quietly died, enlivened by more urgency from the visitors. Some neat passing triangles on the left ended with Callum Robinson stabbing just wide, the ball deflected off a Millwall leg.

Something was stirring. It turned out to be a Sheffield United goal, made by Sharp’s sniping decoy run across the face of the defence. Space opened up in front of Besic, who sensed it, moved forward and then had time to curl a wonderful dipping shot over Bialkowski and into the far corner. It was Besic’s first goal for the club and his first for anyone since October 2018.

It was deserved too, culmination of a spell where the visitors finally found their rhythms, shifting positions, overlapping in unexpected areas, and producing those inventive patterns that have marked Chris Wilder’s team.

Rowett threw on Bradshaw and Wallace for the final 20 minutes. It made little difference. Some fine buildup made space for Norwood to drive low and hard into the corner with six minutes remaining.