Mutch was heavily involved as Campbell deservedly levelled the scores, releasing the former United striker with a fine through-ball which teed up a simple finish past the exposed De Gea. The Spaniard's goal repeatedly came under threat in the remainder of the half, with Campbell, Don Cowie and Peter Whittingham all firing off target, only for United to snatch the lead before the break when Evra powered Rooney's left-wing corner past Marshall.
The Scottish stopper was impressively equal to headed efforts from Fellaini and Chris Smalling in the opening minutes of the second half, but Cardiff soon rallied to disrupt the visitors' flow and almost levelled when Campbell raced onto Tom Cleverley's errant pass, only to chip a delicate effort against De Gea's crossbar.
Scares were few and far between for the champions, and the victory might have been assured if Marshall hadn't smartly saved at the feet of substitute Welbeck, who subsequently half-volleyed just over the bar after a classy one-two with Rooney.
Those misses ultimately proved costly as City substitute Kim headed home Peter Whittingham's left-wing free-kick in the final minute to send the home fans wild with delight. Their celebrations might have been cut short twice in stoppage time, but Rooney's scuffed pass to Welbeck and Smalling's subsequent wayward shot ensured a share of the spoils and a frustrating end to a battling afternoon for the Reds.