On the night Sir Alex Ferguson vowed Manchester United's off-field problems would not deflect his attention from regaining the Premiership title, Middlesbrough sauntered into Old Trafford and did it instead.

Joseph-Desire Job's 80th-minute winner condemned the Red Devils to their fifth defeat of the campaign and left them five points adrift of unbeaten Arsenal.

After recovering from an even worse position at a later stage of last season, no-one at United will be throwing in the towel just yet but if they are to stand any chance of overhauling the Gunners for a second year on the trot, Ferguson knows he must find a solution to the defensive nightmare enveloping his team.

The Scot opted against plunging into the transfer market for a replacement for suspended Rio Ferdinand but in the three games the England international has missed since he started his eight-month ban, United have shipped eight goals, a total it had taken them 10 games to concede prior to the defender's absence.

Juninho's second goal was almost laughable as the little Brazilian was allowed enough space in a crowded penalty area to nod home Stewart Downing's cross.

And though Ruud van Nistelrooy and Ryan Giggs pulled the home side level and Diego Forlan should have snatched a draw with an injury-time header that crashed back off the bar, it would have masked a glaring inadequacy which the manager needs to solve.

The problems so in evidence at Everton last Saturday quickly returned as Franck Queudrue was given the freedom of the near post when he rose to meet Downing's corner but the full-back failed to direct his effort on target.

Unfortunately for the hosts, Juninho was not so profligate. The Brazilian's opener owed everything to his initiative as he followed up Queudrue's bullet strike which squirmed under Tim Howard's body and bounced up onto the crossbar.

As the only man in the vicinity as the ball crashed to earth, he simply could not miss.

His second was a different matter entirely. Juninho guided Downing's cross past Howard and, as a result, in the interval Brown was replaced by Phil Neville.

At least Ferguson's ire would have been sated slightly by van Nistelrooy's 102nd United goal.

The prolific Dutchman is forming an impressive striking partnership with new arrival Louis Saha and though neither man had enjoyed the best of halves, but their telepathic understanding was still in tact as the former Fulham man chested Ryan Giggs' far-post cross into van Nistelrooy's path for the volleyed finish.

Neville's introduction, which saw John O'Shea shift into a central position alongside Mikael Silvestre, did nothing to stabilise a United defence which rocked every time Boro gained a corner or free-kick anywhere within range.

Queudrue nodded a Gaizka Mendieta cross wide, as did Downing, when both were well placed to do far better.

The longer it went on the more ragged it became and after an hour it seemed as though United were falling back on their traditional tactic of piling forward at every opportunity in the hope that their galaxy of stars could muster one more goal than they conceded.

Quinton Fortune smashed a shot into Mendieta, Mark Schwarzer made an excellent double stop to deny Silvestre and van Nistelrooy before Danny Mills scrambled the ball away from Saha, who threatened to latch onto a Neville cross which had been touched on by Kleberson.

The Brazilian was substituted not long afterwards and within seconds of Cristiano Ronaldo being introduced, United were level.

Ronaldo was nothing more than a bystander as Neville delivered a telling cross that van Nistelrooy flicked into Giggs' path.

The Welshman blasted his first shot straight into Mills but reacted quickly to blast the rebound past Schwarzer.

Boro's attacking raids were becoming increasingly rare but at the same time more dangerous as the home side piled forward looking for a winner.

Gareth Southgate, linked with a move to United during the transfer window, produced a brilliant block to send O'Shea's point-blank volley spinning over his own bar after van Nistelrooy had nodded Ronaldo's cross perfectly into the Irishman's path.

A goal seemed destined to come but when it eventually arrived it was for the visitors as Job fired home from the edge of the box.

Forlan struck the bar with a close-range header which he should have converted in the last minute of stoppage time but it would have been rough justice on the visitors.

Teams

Manchester Utd Howard, O'Shea, Brown (Phil Neville 45), Silvestre, Fortune, Kleberson (Ronaldo 63), Scholes, Butt (Forlan 87), Giggs, van Nistelrooy, Saha.

Subs Not Used: Carroll, Fletcher.

Booked: Silvestre.

Goals: van Nistelrooy 45, Giggs 63.

Middlesbrough Schwarzer, Mills, Riggott, Southgate, Queudrue, Mendieta (Parnaby 72), Doriva, Zenden, Downing, Job, Juninho Paulista (Cooper 90).

Subs Not Used: Jones, Maccarone, Nemeth.

Booked: Mills.

Goals: Juninho Paulista 34, 38, Job 80.

Att: 67,346

Ref: P Durkin (Dorset).