The Third Division leaders never looked like surprising their First Division opponents, but for 45 minutes they seemed capable of taking them back to Ninian Park for a replay.
But three goals in 15 second half minutes put paid to that idea and earned last season's semi-finalists another lucrative away-day in the capital.
United had needed two matches, extra time, several postponements and a last-ditch recovery from 3-1 down to dispose of Notts County in the previous round. Yet they began as if they had no intention of making heavy weather of supposedly inferior opposition for a second time and took an early lead, Paul Devlin turning in Vas Borbokis's cross from close range.
But there must have been a bottle of the Cup spirit on Cardiff's team coach, because they bounced straight back. The ball appeared to be running out for a goal-kick when striker John Williams rescued a lost cause with an overhead kick which United goalkeeper Alan Kelly seemed to have covered. But he lost it under Kevin Nugent's challenge and the ball trickled into the net with the goalkeeper lying injured on the ground. The referee, Jeff Winter, was perfectly placed and allowed the goal.
Although they continued to rely on packing their own penalty area, Cardiff produced the best move of an even first half. Richard Carpenter found Mark Delaney on the right and his cross was met by Craig Middleton, but his header flew narrowly wide. The interval gave the United manager, Steve Bruce, a chance to remind his team of the prize at stake. "I had a few choice words at half-time because we hadn't taken the game by the scruff of the neck, and the lads responded well," he said.
Indeed, United began the second half as they had the first, but with better results. Their Brazilian striker, Marcelo, saw his header from Borbokis's cross parried by the Cardiff goalkeeper Jon Hallworth, but David Holdsworth was on hand to bundle the ball over the line and restore his team's lead with his third goal in four games.
Marcelo was the provider again when the 18-year-old substitute Lee Morris struck his first goal for his club, before Graham Stuart rounded off what had become a canter for the Yorkshire side.
The Cardiff manager, Frank Burrows, said afterwards: "We gave away two quick goals and defended sloppily. Playing well for half the game is not good enough, especially against teams two divisions above you."
Sheffield United (4-4-2): A Kelly; Derry, Holdsworth, Sandford, Quinn; Borbokis (B Ford, 59), Stuart, Woodhouse (Henry, 78), Twiss (Morris, h- t); Marcelo, Devlin. Substitutes not used: Jacobsen, Tracey (gk).
Cardiff City (4-4-2): Hallworth; Delaney, Eckhardt, Mitchell, M Ford; Middleton (Hill, 70), O'Sullivan (Legg, 59), Fowler, Carpenter; Williams (Bowen, 59), Nugent. Substitutes not used: Thomas, S Kelly (gk).
Referee: J Winter (Stockton-on-Tees).Reuse content