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.
17. Jack Thomas - Midfielder (unused sub)
Played over 50 times for Stags before dropping into non-league with several clubs including Basford and Ilkeston. Now at Stamford. Photo: .
18. Cameron Belford - Goalkeeper (unused sub)
Belford didn't play a game for Mansfield but has since gone on to play regularly in the lower leagues and in Scotland. Currently at Coleshill Town. Photo: .