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.
13. Fergus Bell - Midfielder
Bell arrived from Monza and played 21 times for Stags before retiring after short spells with Yeovil and Torquay. Is now a property developer. Photo: .
14. John Dempster - Defender (sub)
Dempster spent several years with Stags as player, coach and even manager and is now first team coach at Coventry City. Photo: /
15. Amari'i Bell - Forward (unused sub)
Bell was on loan from Birmingham City but didn't play a minute for Stags whilst at the club. Has had a strong career with Fleetwood, Blackburn and Luton, for whom he played in the Premier League, and is now at Charlton Athletic. Photo: Pete Norton
16. Luke Jones - Defender (unused sub)
Played over 60 times for Stags in two initial spells and then returned in 2014 but a serious injury curtailed his career. Returned two years later to play for Tamworth but is now retired. Photo: ,