SPANISH superkid Jose Antonio Reyes suffered a nightmare on his first Arsenal start as he scored the own goal that sends Middlesbrough to their fourth major Cup final in seven years.

Boro manager Steve McClaren laid to rest his hoodoo against Arsene Wenger's side, avenging the FA Cup semi-final defeat by the Gunners at Old Trafford two seasons ago.

Gianluca Festa's own goal was the difference then and, by an amazing quirk of fate, it was one from Arsenal that settled the issue last night.

Amid scenes of high drama at the Riverside, £17m signing Reyes inadvertently found the wrong end five minutes from time when he went for the same ball as Stuart Parnaby.

The Boro defender, a 64th-minute replacement for Jon Greening, claimed the goal but replays showed it was Reyes who connected after Parnaby prepared to shoot having been set up by Juninho.

Boro's Brazilian talisman had scored the goal at Highbury a fortnight earlier that gave his side the slimmest advantage going into the second leg of this Carling Cup semi-final.

And Bolo Zenden doubled their lead in the 69th minute when coolly lifting the ball over goalkeeper Graham Stack after Gaizka Mendieta had slipped a first-time pass into his path following good work on the left by Massimo Maccarone.

Boro's £8.15m record buy had been the villain of the piece, squandering two glorious chances before Arsenal were dealt a massive blow when veteran defender Martin Keown was sent off for a professional foul on the Italian on the stroke of half-time.

But the ten-man Gunners still managed to pull a goal back in the 77th minute when skipper Patrick Vieira headed against the woodwork from a corner and Edu nodded in the loose ball.

Reyes' intervention, however, triggered wild celebrations on Teesside and McClaren's men will now make their first appearance at Cardiff's Millennium at the end of the month when they attempt to land the first major trophy in their 128-year history against Bolton Wanderers.

Former England international Keown was dismissed for the 13th time in his career. Juninho played the through-ball and the 37-year-old centre-half inexplicably turned his back on it. Maccarone made the most of a kind ricochet, but he literally couldn't escape the clutches of Keown and referee Dermot Gallagher had no hesitation in raising the red card.

This was only Arsenal's second defeat in 33 domestic League and Cup games - and both have been at the hands of Boro.

Now the Teessiders are League Cup finalists for the third time in seven years.

Boro were without the combative qualities of George Boateng in midfield after he succumbed to a groin problem, and Greening was drafted in for his first appearance since the Boxing Day defeat here by Manchester United.

In defence, Ugo Ehiogu was still out with a groin strain, but skipper Gareth Southgate was passed fit after suffering a minor reaction in the 3-0 win at Leeds to a hamstring injury, and on-loan Danny Mills returned after sitting out Saturday's game against his parent club.

Arsenal showed eight changes from the side that started Sunday's 2-1 defeat of Manchester City at Highbury, and three from the first leg against Boro a fortnight earlier.

The most notable addition was Reyes, who was handed his full debut after making his bow as a substitute against City.

Reyes, 20, and signed from Sevilla, is regarded as the most outstanding young talent of his generation in Spain.

And it was immediately clear that Boro were aware of his reputation, with Southgate penalised in only the second minute for bringing him down.

Arsenal were playing keep-ball as they pinned Boro back in their own half in the first three minutes.

But when Keown slipped just inside his own half, Juninho - yesterday named in the Brazil squad for the game against the Republic of Ireland in Dublin in two weeks' time - seized on the error and made for goal.

Kolo Toure went in pursuit and when Juninho attempted to deliver a low cross, the right-back managed to deflect the ball wide at the expense of a corner which came to nothing.

Vieira picked out Gael Clichy with a crossfield ball, but although the Frenchman outjumped Mills, his header looped well over.

Edu then unleashed a 30-yard piledriver which fizzed just wide after Chris Riggott was guilty of a sloppy clearance.

The Brazilian then headed wide from David Bentley's inswinging corner as the visitors maintained the pressure.

Maccarone's first chance, in the 17th minute, was by far his best. Ashley Cole diverted the ball into his path after challenging Juninho, but with only Stack to beat, Maccarone steered his shot wide of the target.

The Italian's angst showed when he committed a late tackle on Cole and was lucky to escape a caution.

Reyes then made a mug of Mills, much to the delight of the travelling fans who will forever resent the England international's attempt to psyche out Thierry Henry as he was about to take a penalty, in the Premiership game at Highbury which marked the first of four meetings between the sides in this 24-day series.

But having done the hard part, Reyes produced a timid finish which went straight at keeper Mark Schwarzer.

Boro then hit a purple patch but couldn't capitalise on two more gilt-edged chances.

Gaizka Mendieta was fouled by Clichy and when Zenden hoisted the free-kick to the far post, Franck Queudrue pulled the ball across goal for Maccarone who, deep inside the six-yard box, dragged it from behind him but looked on in agony as Stack scrambled his effort off the line.

There was further frustration for Boro when Zenden centred from the left and Riggott, Maccarone and Juninho all failed to apply a finishing touch as the ball flew across the face of goal.

The loss of Keown for Arsenal was followed by that of Edu, who was stretchered off in first-half stoppage time after falling awkwardly.

But he reappeared for the second half and had an instant influence in a controversial incident when Reyes chased his pass before going down in the area under the challenge of Schwarzer.

Arsenal launched vehement appeals for a penalty, but Mr Gallagher was unimpressed, the home fans chanted cheat, and replays showed that Reyes had hurdled the prostrate keeper.

Boro enjoyed a let-off when Southgate performed a desperate goalmouth block from Toure in the 53rd-minute.

Riggott and Queudrue were booked for fouls - the Frenchman now misses the game at Newcastle later this month for his fifth yellow card this term - as Boro resorted to the strongarm approach to resist the Gunners. But the goal they had threatened finally arrived to leave the Riverside in a state of ferment.

Arsenal's David Bentley certainly became a little overwrought when he jumped into Juninho, who reacted by pushing the teenager before the referee stepped in to book the winger.

Schwarzer performed a full-length save to deny Vieira and, at the other end, Pascal Cygan made a crucial interception to foil Joseph-Desire Job, who had come on as a 70th-minute replacement for Maccarone.