Nigel Clough’s side were trailing when Mathieu Baudry headed home a corner from Dean Cox on 71 minutes.
But up popped Bob Harris to restore parity six minutes later and a point for the Blades.
Chesterfield also confirmed their place in the top six, after Rochdale’s defeat to MK Dons.
Elsewhere in League One, Doncaster Rovers lost 2-1 at Notts County.
The hosts were 2-0 up with goals from Thompson and Noble, before Nathan Tyson snatched a late penalty.
In League Two, York City lost 2-0 at home to Newport.