Roy Keane's long-awaited return could not prevent Manchester United sliding to a defeat at Middlesbrough that leaves them seven points behind Arsenal.

Keane made his first start since 31 August but former Old Trafford assistant Steve McClaren outwitted his old mentor Sir Alex Ferguson to inflict United's second Christmas defeat.

It's a bad scoreline considering the amount of possession we had Man Utd boss Sir Alex Ferguson

Goals either side of half-time from Alen Boksic and Szilard Nemeth left United chasing a game they failed to catch.

United laid seige after Ryan Giggs pulled one back but were caught as Joseph-Desire Job sealed the points.

Keane initially eased himself back into action in a holding role in midfield, where he struggled to have an influence on procedings.

Boro's big day

43mins: Boksic puts Boro ahead. 47mins: Nemeth doubles the lead. 60mins: Giggs pulls one back for Man Utd. 86mins: Job seals Boro's victory.

An open first half saw the action swing from end-to-end, although initially both sides attacks broke down on the edge of the opponents' penalty area.

Boro keeper Mark Schwarzer was first forced into serious action on 36 minutes when he plunged to his right to beat away John O'Shea's thumping shot.

Paul Scholes is under pressure from Mark Wilson

At the other end Alen Boksic broke clear with Manchester United looking for the offside flag and was denied by Barthez's legs.

Boksic had better luck five minutes later as he again flirted with the offside flag to collect Franck Queudrue's pass and clip the ball over his former Marseilles team-mate Barthez for only his second goal of the season.

Any hopes United harboured of a quick riposte after the break were dented three minutes into the second half by Szilard Nemeth.

We we wanted to go into the new year with our home record intact Boro boss Steve McClaren

The Slovakian international collected a headed clearance 25 yards out and all too easily brushed off O'Shea to go on and bury his shot past Barthez.

O'Shea was found wanting again two minutes later when he allowed Boksic to get goal-side and latch on to Queudrue's long ball, but this time the Croatian's attempt to lob Barthez landed on the roof of the net.

The visitors's were denied a penalty when former Manchester United midfielder Mark Wilson handled in the penalty area.

And Boro had an escape when Gareth Southgate swung a wild boot at Veron's low cross and just avoided slicing the ball into his own net.

It was game on with 30 minutes left when Ryan Giggs got in front of Ugo Ehiogu to meet Solskjaer's cross and guide the ball into the net.

Boro's Geremi has John O'Shea and Roy Keane for company

David Beckham came off the bench to line up a free-kick 25 yards, only for his shot to deflect wide off Boro's defensive wall.

United laid seige to Boro's goal but were caught by a sucker punch as Massimo Maccarone nodded a cross into the path of Job to tap the third in four minutes from time.

Watch a round up of the Boxing day Premiership action

Middlesbrough: Schwarzer, Queudrue, Ehiogu, Southgate, Parnaby, Greening, Wilson, Job, Geremi, Nemeth (Maccarone 83), Boksic (Wilkshire 63).
Subs Not Used: Vidmar, Windass, Crossley.

Booked: Job.

Man Utd: Barthez, Gary Neville (Beckham 72), Blanc, Brown, O'Shea (Ferdinand 83), Giggs, Keane, Veron, Scholes, van Nistelrooy, Solskjaer. Subs Not Used: Phil Neville, Ricardo, Forlan.

Booked: Scholes.

Attendance: 34,673

Referee: G Barber (Hertfordshire).