Alex Ferguson had unmistakably thrown down the challenge yesterday, warning that he would be "examining in every detail the attitudes and standards" of a Manchester United side whose Premiership challenge has been undermined too often by the rival attractions of the Champions League.

Even such notably hard taskmasters can purr with delight on occasions and Ferguson was delighted by this response. There is no more passionate challenge to United than that provided by their rivals from across the Pennines. They had to stretch every sinew, burst every lung before victory was achieved.

This was Leeds's Nou Camp. Manchester United might have gained plaudits for a thrilling midweek draw in Barcelona but Leeds sensed the opportunity to cause further embarrassment to a side whose Premiership lapses, according to Ferguson had been "unacceptable". The manager having drawn the line, his players defended it to the last man; they had to.

Only 12 minutes remained of an enthralling contest when United summoned the winning goal that swept them back into second place, with Aston Villa's lead now only a point.

Appropriately it fell to Nicky Butt, precisely the sort of fringe senior player at whom Ferguson's words had been most directed, his first goal of the season coming as he swivelled just inside the area to beat Paul Robinson with a rasping drive. "He has had a mixed season but today he was our best player," Ferguson said. "`Nigel Martyn made two great saves to deny him, but he got the winning goal due to his perseverance. It was a fantastic result for us, and the most entertaining game I've ever known against Leeds at Old Trafford."

Leeds, finally, were spent, but their first away defeat in the Premiership this season brought upon them considerable credit, as they were disturbed defensively by injuries to Martin Hiden, who may be absent for a month with knee ligament trouble, and to their goalkeeper Nigel Martyn, who succumbed to a back injury after an outstanding first half in which he pulled off as many breathtaking saves - three - as Andy Cole spurned chances.

Butt had looked in disbelief at the best of these saves; with the game still goalless, Martyn leapt prodigiously to claw his header on to the bar, sustaining his back injury as he fell on to his far post.

In Ferguson's search for "freshness" this was a United side with their wings clipped: no Beckham, no Blomqvist and Ryan Giggs only appearing as a second-half substitute. Leeds drew encouragement, tackling ferociously in central areas and breaking in numbers, their strikers Harry Kewell and Jimmy Floyd Hasselbaink back to their sharpest.

Leeds survived Ole Solskjaer's appeals for a penalty, when he fell under Gunnar Halle's challenge, before Hasselbaink provided them with a half-hour lead. Entirely unrecognisable from the crabby, flabby figure of a few weeks ago, Hasselbaink drove determinedly in from the left and his powerful low shot careered into the net off the inside of the near post.

Martyn winced in pain at every drop kick, patted balls at his feet into touch in near despair and saved excellently from Solskjaer and Cole in between swigging down a couple of painkillers hurried round by his manager, David O'Leary. His last duty, though, was to pick the ball from the net, Solskjaer receiving Dwight Yorke's pass to beat him with a low, angled drive.

For Martyn to survive the half was one thing, to emerge for the restart practically impossible. He gave way to his teenage understudy, Robinson, who, through no fault of his own was beaten within 10 seconds of the restart, Roy Keane side-footing into the roof of the net after Paul Scholes had sped outside Ian Harte.

That Leeds could summon another response in the face of such mounting casualties seemed unlikely, but within six minutes they were level.

Kewell, full of vim throughout, capitalised upon an error by Wes Brown and his left-foot finish over Schmeichel was delightfully composed. Robinson's saves then kept Leeds alive until the moment that brought Butt's season alive.

Manchester Utd: Schmeichel, G. Neville, Stam (Berg 76), Butt, Cole (Giggs 64), P. Neville, Keane, Scholes (Sheringham 72), Yorke, Solskjaer, Brown. Subs Not Used: Van Der Gouw, Curtis. Booked: P. Neville. Goals: Solskjaer 45, Keane 46, Butt 77.

Leeds: Martyn (Robinson 45), Haaland, Hasselbaink, Ribeiro (Smith 85), Hopkin, Halle, Kewell, Harte, Hiden (Wetherall 25), Woodgate, McPhail. Subs Not Used: Wijnhard, Granville. Booked: Ribeiro, Haaland. Goals: Hasselbaink 29, Kewell 52. Attendance: 55,172.

Referee: G Poll (Tring).