Goals from Alen Boksic and Szilard Nemeth either side of half-time gave Boro the advantage, and although Ryan Giggs pulled one back on the hour, Joseph-Desire Job made sure of the points five minutes from time to condemn United to a second successive Premiership defeat.

It was the third time McClaren has turned the tables on former boss Sir Alex Ferguson since leaving Old Trafford for the north-east two summers ago, and preserved an unbeaten home run of 11 matches this season.

But even more importantly for Boro, the game saw their under-pressure strikers finally return to the goal trail as Boksic collected only his second of the season with Nemeth and Job also scoring.

Roy Keane's return to the starting line-up for the first time since August 31 was the talk of the Riverside Stadium as the home fans pondered on just how their central midfield duo of former United men Jonathan Greening and Mark Wilson, in for the injured George Boateng, would cope with the threat of the Irishman and his Argentinian partner Juan Sebastian Veron.

The answer, at least in the early stages, was that they would manage it reasonably well.

United played some neat passing football without really threatening to get behind a Boro rearguard superbly marshalled by skipper Gareth Southgate and Ugo Ehiogu, while the home side always posed a threat on the break, but crucially, not in the right areas.

But as Keane started to find his feet once again and Giggs and John O'Shea got the bit between their teeth down the left, the signs started to grow increasingly ominous.

However, Ruud van Nistelrooy and Paul Scholes, playing in the hole behind the Dutchman, never saw enough of the ball to cause the alarm bells to ring for any great length of time, and it was eventually full-back O'Shea who reminded Mark Schwarzer that he might have to earn his wage packet.

Gary Neville intercepted Geremi's misplaced 37th-minute pass and found Scholes on halfway, and he in turn played the ball into the path of the rapidly-advancing Irishman.

O'Shea looked up before cutting inside and unleashing a powerful right-foot effort which Schwarzer did well to palm away.

Boksic had a fine opportunity to capitalise on the Australian's work two minutes later when the offside flag stayed down as he raced on to Greening's pass, but he only succeeded in shooting against Fabien Barthez's legs.

But the United defence paid the price a minute before the break.

Full-back Franck Queudrue was allowed to charge from deep inside his own half before slipping a pass through a static rearguard for Boksic to chip delicately over the Frenchman to open the scoring.

But if the opening 45 minutes had produced little goalmouth action, the stakes were raised after the break.

It took Boro just three minutes to increase their lead, Nemeth pouncing on indecision in the United back four to hold off O'Shea and thump a close-range shot past Barthez to send the home crowd into raptures.

The Teessiders could have extended their lead further on 50 minutes when Boksic lifted a lob from Queudrue's pass over the advancing keeper but also over the crossbar, and Job had the Frenchman scurrying across his goal with a curling left-foot effort.

However, the resilience which has served United so well over the years came to the fore on the hour when Giggs timed his run to perfection to meet Ole Gunnar Solskjaer's cross in front of goal and flick the ball past Schwarzer to breathe new life into the contest.

As United started to turn the screw, Boro found themselves pinned back inside their own half, and their fears increased with 18 minutes remaining when Ferguson replaced full-back Neville with England skipper David Beckham.

Beckham saw a 77th-minute free-kick deflected wide and then watched another goal-bound effort clip a Boro defender and drop wide nine minutes from time after Giggs drove a corner to his right foot.

But just as it looked as though Boro might crack, substitute Massimo Maccarone headed Geremi's cross back across goal for Job to cement victory in style.

United manager Sir Alex Ferguson blmaed a lack of concentration for his side second successive defeat.

'Well, 3-1 is a bad scoreline considering the possession of the ball we had

and I think in the first-half, we've really thrown it away, the amount of

possession we had and the great opportunities at the edge of their box,'

Ferguson told Sky Sports.

'We just didn't have the concentration to capitalise.

'They've got a breakaway in the last minute of the half and then right

immediately after half-time, we lost another goal, and it made it an uphill

fight.

'We got one back and we threw everything to the wind, but when you do that,

there's always a danger you might lose a third one, which we did.'

Ferguson, who handed skipper Roy Keane a first start since August 31,

introduced David Beckham and Ferdinand as late substitutes in a bid to find an

equaliser, but was made to pay for his bold move.

'When you're trying to claw something back from a game, it's always worth

trying,' he said. 'We've done that many times in the past.

'Steve Bruce has ended up there, Gary Pallister. Over the years, we've done

that many times. Laurent Blanc did it last season a couple of times and I think

it's always worth a risk to get a point.'

Ferguson's former number two Steve McClaren was understandably delighted.

'What a performance,' he beamed. 'The players were magnificent. I couldn't fault them.

There have been many great performances, especially this season, but that was

very, very good.

'We've played these teams at home before and we've had a slice of luck, but

today, the performance justified the result, although we came under pressure

towards the end, which you're bound to.

'But we defended very well and I thought we deserved the win. It's three

massive points. We needed that result.'

United's defeat, coupled with leaders Arsenal's victory at West Brom, created

a gap of seven points between last season's top two, but McClaren believes there

are plenty of twists and turns to come before the title race reaches its

conclusion.

'This league is strange,' he said. 'Everybody is beating everybody else.

You look at West Brom and you think that would probably be an easy game for

Arsenal.

'Everybody seems to be in very good home form and there's nobody pulling away

from anybody else. All anybody has to do is put together a good run - and there

are plenty more games to go.'