It’s the first time the two teams have played each other since August 13, 2014, when the Blades hosted Mansfield in a League Cup first round tie when the sides were in League One and League Two respectively.
Ironically, the United manager that night was Nigel Clough, who is now of course the Stags boss.
Andy Butler put the Blades ahead seven minutes into the second half, heading home a Ben Davies corner.
Clough’s relief was short-lived, though, as Alex Fisher brought Mansfield level just four minutes later with a powerful right-foot shot.
The Stags then pushed for a winner, with Blades goalkeeper Mark Howard keeping out a Sam Clucas effort.
But Marc McNulty popped up with a last-gasp winner to delight Clough with four minutes left and set up a clash with West Ham in their second round tie.
Here, we look at who played for Mansfield that day and then where their careers took them after leaving Stags, with some of them pictured during the game itself.
5. Ritchie Sutton - Defender
Sutton played over 150 games for Mansfield before heading to Tranmere and then numerous clubs in non-league. Is now a protection adviser in the insurance industry. Photo: .
6. Ryan Tafazolli - Defender
Had long spells with Peterborough and Wycombe after leaving Stags and is now at Swindon Town having had a brief spell in Hong Kong. Photo: Clive Brunskill
7. Chris Clements - Midfielder
Five years at Stags were followed by spells with clubs including Grimsby and Cheltenham, and he's currently with Racing Club Warwick. Photo: ,
8. Simon Heslop - Midfielder
Heslop has played for several other league and non-league clubs since leaving Stags and is still playing at Pickering Town. Photo: Clive Brunskill