Middlesbrough ruined Manchester United's Christmas, and Roy Keane's return to their starting line-up, with a 3-1 victory to maintain their unbeaten record at the Riverside fortress.
After a blistering run of seven straight wins in the league, United have now suffered back-to-back defeats and are once more losing touch with Arsenal - who beat West Brom 2-1 to pull seven points clear of United, and four ahead of Chelsea.
Keane was starting his first Premiership match since being sent off in the August 31st draw at Sunderland. But even the presence of their talismanic club captain could not inspire United as Boro capitalised on two superbly-taken goals by their much-criticised strikers.
Alen Boksic was first to strike, right on half-time. French wingback Franck Queudrue created the opening with a mazy run in from the touchline and a beautifully weighted pass in behind a back-four missing the injured Mikael Silvestre.
Boksic arrived at the ball a fraction ahead of Fabien Barthez and elegantly lifted it over the French goalkeeper to put Boro in front.
Nemeth then delivered a killer punch just three minutes after the restart.
Picking up a loose ball on the edge of the box, the Slovakian wriggled his way past Laurent Blanc and beat Barthez with a fierce shot at his near post.
United hit back on the hour when Paul Scholes found Ole Gunnar Solskjaer on the right. His low cross allowed Giggs to slot past Schwarzer from close range and set up a grandstand finish.
But just as it looked as though Boro might crack, substitute Massimo Maccarone headed Geremi's cross back across goal for Joseph-Desire Job to pop the ball into the net five minutes from time and secure the win.