Red Devils crumble late on
Rooney tussled for possession with Jordon Mutch in the early stages of Sunday's game at Cardiff City Stadium, then kicked the 21-year-old midfielder in frustration, only to be shown a yellow card by referee Neil Swarbrick.
That decision to leave Rooney on the pitch proved costly for the hosts on 15 minutes, when Ben Turner's loose pass fell to Antonio Valencia, whose cross from the right flank was flicked by Javier Hernandez into the path of Rooney, whose shot deflected off Gary Medel's boot before flying into the net.
Cardiff, who beat Manchester City 3-2 earlier this season, weren't intimidated by their opponents or going behind, though, and equalized following a fine, flowing move on 33 minutes. Peter Whittingham's pass found Mutch, who slotted a sliderule pass to Fraizer Campbell, who in turn sidefooted the ball past David De Gea with a clinical first-time finish.
Campbell, playing against his former employers, fired over the crossbar from 12 yards before Whittingham also steered a half-volley over.
But United went ahead once again on the stroke of half-time, when a Rooney corner from the left was headed home by Patrice Evra, who lost his marker in the box to steer his effort past David Marshall.
After the interval, Marshall pulled off two superb saves to keep the score at 2-1, first diving at full stretch to palm Fellaini's flicked header from a Rooney free-kick away for a corner, then denying Chris Smalling from close range.
It was nearly 2-2 on 54 minutes, though, when Tom Cleverley's loose pass-back was seized upon by Campbell, who chipped the ball over De Gea from 18 yards only to see his superb effort smack the crossbar.
David Moyes threw on Danny Welbeck and Ryan Giggs for Adnan Januzaj and Hernandez in a bid to gain more control of the game, and Welbeck combined brilliantly with Rooney on 80 minutes, only to steer a fiercely-struck half-volley inches over the crossbar.
Craig Noone, Bo-Kyung Kim and Andreas Cornelius all came on for Cardiff and United looked like they were going to hold on for all three points.
But Kim sent the home fans into raptures when he planted a firm stoppage-time header from a free-kick past De Gea to earn Cardiff a deserved point.