Cardiff's hopes of securing automatic promotion to the Barclays Premier League were left hanging by a thread as they suffered a 3-0 defeat to Middlesbrough at Cardiff City Stadium.
The Bluebirds had entered this game third in the npower Championship, a point behind Norwich with both sides having two games to play.
But their hopes of putting pressure on the Canaries were dashed as a woeful first-half display saw Boro open up a 3-0 lead inside 21 minutes as Leroy Lita's 99th career goal and further strikes from Barry Robson and Richard Smallwood put Tony Mowbray's men in total control.
The result condemned Cardiff to their heaviest home loss since their final match at Ninian Park against Ipswich in April 2009, and meant a win for Norwich in their late game at Portsmouth - or, failing that, at home to Coventry on Saturday - would seal their promotion at the expense of the Bluebirds.
Cardiff look set to face another play-off campaign, unless the FA elect to mete out a heavy punishment to QPR over their signing of Alejandro Faurlin when the outcome of that disciplinary process is announced later this week.
The Bluebirds got off to a nightmare start as McMahon's long diagonal ball found Lita, and the striker's well-placed header beat the despairing dive of Tom Heaton to find the corner of the net with less than three minutes played.
Cardiff sought a quick response with captain Craig Bellamy's cross just evading JLloyd Samuel, but moments later they were 2-0 down as their hopes of automatic promotion continued to fade.
Lita was given far too much space on Middlesbrough's right-hand side and his measured pass allowed skipper Robson to guide the ball into the far corner after 13 minutes.
And the game was as good as over after just 21 minutes as Boro found the net for a third time.
A neat exchange between Robson and Marvin Emnes sent the striker into space. Enmes cut in from the right to pull the ball back and find Smallwood for the midfielder to fire beyond a flat-footed Heaton to the astonishment of the home support.
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