Iliman Ndiaye was the matchwinner for the Blades, coming off the bench to score a superb solo goal to help down a Spurs side who barely got out of first gear at a rowdy Bramall Lane.
Boss Paul Heckingbottom said: "We've had a top side come here and we've put on a good performance. We've spoken about treating the league and cup separately; there's a tension and an anxiety in the league and there's been a different feel in the cup. We want to play with that freedom, but we also want to win."
Here’s how we rated United’s players as they sealed progression to the last eight of this famous old competition ...