Sheffield United might be the masters of 3-5-2 but Millwall won't roll out the red carpet

Admitting United have perfected a system which revolves around the use of two attacking centre-halves, the 27-year-old admitted to being fascinated by the tactics which, after steering them to the League One title three seasons ago, also saw them gain promotion from the Championship last term.

“They are the masters of the 3-5-2, with the overlapping centre-halves, so it will be a great test,” Wallace said. “They are a Premier League team, doing really well, so it’s going to be a real challenge.”

Although Chris Wilder’s strategic skills have won him an army of admirers, including Manchester City’s Pep Guardiola and Liverpool’s Jurgen Klopp, Gary Rowett has also been showcasing the cerebral side to his nature since taking charge at The Den three months ago.

Having lost only once in all competitions since November, Millwall frequently set up in a 5-2-3 formation and the battle of wits on the touchline could go a long way towards deciding the outcome of Saturday’s contest; particularly if, as expected, Wilder chooses to change his starting eleven.

United set up their trip to London after beating AFC Fylde 2-1, and although the margin of victory was perhaps slimmer than many expected, Wilder was encouraged by the way the likes of Jack Rodwell and Ben Osborn grasped the key principles of his masterplan.

Millwall, eighth in the Championship, progressed to the next stage of the competition following a 3-0 win over Newport County and Wallace, previously of Huddersfield Town and Scunthorpe, said: “These are the sorts of games you want to play in.

“I’m just looking forward to seeing if we can pack The Den out again and really get the atmosphere going.”

Millwall’s record signing Ryan Leonard, who moved to the capital from United, has returned to training ahead of the fourth round tie following injury but is unlikely to face his former club.