Sheffield United: James Shield identifies the key moments from today's game against Millwall

Key Moment: United had wrestled the advantage and were gaining momentum when, midway through the first-half, they were awarded a penalty.

Usually one of the most intimidating grounds in English football, Millwall's poor run ahead of this match meant The Den had been almost funereal until that point.

But when Billy Sharp saw his spot-kick pushed onto the crossbar by Ben Amos, the atmosphere changed on both the terraces and the pitch with the home supporters roaring their players forward who, as if by magic, gained an extra spring in their step.

The key moment, or key period, came when Jake Cooper and Lee Gregory had cancelled-out Sharp's opener. Squads with less self-belief would have folded but United kept going through the process, kept adhering to their game plan and were rewarded when David McGoldrick scored twice during the closing stages.

Key Man: Naturally, given the fact he is still on loan at the club from United, all eyes were on Ryan Leonard both before and during the game.

An early and, in fairness, deserved yellow card for a late scything challenge on McGoldrick forced the midfielder to curb his tenacious streak.

Although John Fleck edged their duel in midfield for most of the afternoon, Leonard still made his presence felt and produced the pass that sent Gregory scampering through for Millwall's second.

Manager Chris Wilder gave honourable mentions to Enda Stevens and Kieron Freeman while McGoldrick will inevitably steal the headlines. But Mark Duffy was at the heart of all United's best work.

How the Game was won: The answer is through sheer determination, self-belief and persistence. Despite being on top for the most part, United seemed destined for defeat after a mad three minutes early in the second period.

But their ability to keep cool heads and follow Wilder's tactical instructions highlighted their growing experience and maturity.

Referee Watch: He angered the home crowd with his decision to award United a 25th minute penalty which Sharp missed when Ben Amos produced an excellent save to turn on to the crossbar.

He annoyed United too midway through the second period when John Fleck, bearing down on the Millwall penalty area, saw his progress halted following a foul on Mark Duffy.

But, for the most part, Andy Davies and his assistants made the correct decisions and allowed the match to flow as much as it possibly could.

Summary: Completing tests of character at home, as United did against Preston North End last weekend, is one thing.

Passing them with flying colours at The Den, one of the toughest grounds in English football for visitors to come and play, is another.

Speaking afterwards, Wilder brushed aside questions about United's potentially costly lapses in concentration  - "We've just won the game" - although he is bound to address the matter with his squad when they report back for duty on Monday.

But it was pleasing and promising to see United secure what, on reflection, was a deserved victory by keeping their heads.

Yes, they attacked. Yes, they increased the tempo when there was an opportunity.

But there was no 'charge of the light brigade'. No desperation creeped into their play. Instead, they remained cool, calm and collected. In, what Wilder admitted, is a very difficult arena.