Kieffer Moore scored two superb goals as Championship leaders Sheffield United won at Cardiff City to plunge the Welsh club into the relegation zone.
After a drab and goalless first half, the Blades moved up a gear in the second as Moore controlled Alfie Gilchrist's cross with his chest before firing into the top corner.
The strike was as memorable as the rest of the game was forgettable, and the Wales forward scored a second against his former club eight minutes later as he drilled in a low effort from the edge of the penalty area.
Moore's goals were a fine riposte to being booed by the Cardiff fans who once adored him, and the result maintains the Blades' three-point cushion at the top of the Championship.
As for the Bluebirds, an eighth match without victory means they will spend Christmas in the bottom three, two points adrift of safety.
The day had not started well for Cardiff, with wins for Portsmouth and Hull City in the day's earlier games dumping the Bluebirds back into the relegation zone.
Considering their opponents' imperious form – the Blades were on a 10-match unbeaten run which included eight victories – there was little to suggest that this would be the day when Cardiff would earn their first win in eight attempts.
They barely saw the ball early on as United kept possession with the ease of a training exercise, which gave them control of the encounter albeit without creating much in the way of chances.
A low-key first half produced no shots on target but there was one from each side within 10 minutes of the restart.
Tom Davies had United's, forcing Jak Alnwick to palm the ball away, before Cardiff's Yakou Meite had Michael Cooper diving smartly to his left.
The Blades were starting to get a firmer grip on the game at this stage, and they took the lead in spectacular fashion as Moore held off Jesper Daland to bring down Gilchrist's cross from the right and crack a left-footed strike back across goal and into the net.
The Wales striker used his right foot to equally good effect eight minutes later, guiding a low 20-yard effort past the near post to double his team's lead and silence the boos that had come from the supporters of his former club.
There were still some jeers at the final whistle but those were for Cardiff, who are deep in the relegation mire for a third season out of four.
Cardiff City: Alnwick ©, Daland (Kanga 83’), Chambers, Goutas, Bagan, Rinomhota, Robertson (Kpakio 83’), Siopis, Willock (R. Colwill 48’), El Ghazi (Robinson 72’), Méïté (Ashford 83’). Subs not used: Horvath, Fish, T. Davies, Perrett.
Sheffield United: Cooper, Gilchrist (Baptiste 83’), Souttar, Hamer, Moore (McCallum 74’), O’ Hare, Rak-Sakyi (Brewster 62’), Burrows, Robinson © (Norrington-Davies 83’), Davies, Peck. Subs Not Used: Davies, Marsh, Brooks, Oné, Blacker.