Former Aston Villa midfielder Peter Whittingham destroyed United with a clinically taken hat-trick as Cardiff continued their push towards the Championship summit.
The Sheffield side, playing with a passion that was lacking in their recent visits to Scunthorpe United and Blackpool where they conceded six goals, pressed again with Anthony Gerrard once more the saviour, sliding in to rob Darius Henderson on the goal-line as the striker waited to pounce on Keith Treacy's precise cross.
Ched Evans tried his luck with a speculative strike from long range, the ball flashing over the target before the game erupted in a blistering seven-minute spell.
Cardiff broke the deadlock in the 41st minute when Chris Morgan's clearance hit James Harper, the ball falling kindly to Jay Bothroyd who finished from close range.
United were level a minute later in similar fashion, Glen Little's cross bouncing off centre-back Mark Hudson as Darius Henderson lashed the loose ball into the far corner from 12 yards.
The Welsh side nosed in front again in the 45th minute, Henderson grappling with Bothroyd as the pair stretched to meet Adam Matthews' long throw. Whittingham stepped forward to coolly dispatch the spot-kick for his tenth of the season.
The drama continued as United pulled level two minutes into time added on. David Marshall clawed away a close-range effort from Evans but only to the lurking Henderson whose header looped beyond the keeper and into the net.
Whittingham added the Bluebirds' third goal in the 60th minute after United failed to defend another Matthews long throw. Gerrard flicked the ball to the Cardiff midfielder who finished in clinical fashion from eight yards.
Matthew Kilgallon fired a left-foot strike over the top and Henderson almost found a way through before Whittingham killed off the Sheffield side five minutes from time, with a flowing move.
Michael Chopra picked out Bothroyd whose low pass was steered past Ian Bennett from the tightest of angles. Midfielder James Harper stabbed home United's third in the dying minutes and Stephen Quinn had the ball in the net seconds from time only to be ruled offside.