Manchester United piled on the agony for Arsene Wenger as Arsenal's rapidly deteriorating season took another blow with defeat in the FA Cup quarter-final at Old Trafford.Fabio da Silva and Wayne Rooney struck in each half to take Manchester United to Wembley with a victory that sent Arsenal crashing out of a third major competition inside a fortnight.United boss Sir Alex Ferguson, who rounded defiantly on his critics in his programme notes, demanded a response from United after Premier League defeats at Chelsea and Liverpool.And a team that included seven defenders in a reshuffled starting line-up delivered the win he craved.Arsenal followed the predictable pattern of many recent meetings with United by controlling possession for long periods but failing to take advantage.Their FA Cup exit followed the Carling Cup final defeat to Birmingham City and the contentious Champions League loss to Barcelona last Tuesday.When they did pierce United's rearguard, the Gunners found veteran goalkeeper Edwin van der Sar in outstanding form - he denied Robin van Persie in the first half as well as saving well from Laurent Koscielny, Marouane Chamakh and Tomas Rosicky after the interval.Wenger's problems increased as defender Johan Djourou was stretchered off late on after he appeared to collide with team-mate Bacary Sagna as he attempted to stop Javier Hernandez adding a third for United.Ferguson will be satisfied that United's season has moved closer to being back on course with a vital triumph and the boost of a Wembley appearance, but counterpart Wenger cut a dejected and despairing figure at the final whistle.Arsenal still have the Premier League title to aim for, but Wenger must sift through what may well be heavy psychological blows to his players as three targets have been removed from their sights in swift succession.Wenger always hails the mental strength contained within Arsenal's squad - and that faith and resolve will now be tested to the full after a nightmare spell.Ferguson's starting line-up carried an unfamiliar look - but his side performed in highly effective fashion, despite Arsenal enjoying a large share of possession in the first 45 minutes.Brazilian brothers Rafael and Fabio were relieved of their familiar defensive duties and utilised wide on the flanks, a ploy that should have brought United an early lead.Fabio's cross from the left was an open invitation for Rafael to score but he headed wastefully over the top from close range.Fabio did not make the same mistake when presented with the chance to give United a crucial advantage after 27 minutes.Rooney's delicate cross was met by Hernandez and when his header was pushed out by Manuel Almunia the youngster slid in to prod the rebound into the roof of the net.Van Persie led the Arsenal response with a low angled effort that was turned around the post by Van der Sar, then heading just wide from the resulting corner.There was a welcome sight for United and their supporters at the start of the second half as Antonio Valencia returned as a substitute for the first time since breaking his leg in the Champions League tie against Glasgow Rangers at Old Trafford in September.United keeper Van der Sar kept them on terms with an instinctive double save right after the break, twice denying Koscielny after he linked with Van Persie inside the area.The value of Van der Sar's saves was quickly illustrated as Rooney doubled United's lead shortly after.Rafael was instrumental with a surge into the area and when another Hernandez effort was blocked Rooney pounced to head home.Arsenal once again resumed territorial advantage but simply could not find a way past Van der Sar, who distinguished himself with further fine saves from substitute Chamakh's header and Rosicky's swerving 20-yard shot.As Arsenal pushed forward in desperation, they inevitably left spaces at the back and United almost cashed in as Almunia clawed out a shot from Hernandez.Defender Djourou was injured in the scramble and was stretchered off after lengthy treatment - during which he was given oxygen - that left eight minutes of stoppage time.Manchester United substitute Paul Scholes enlivened proceedings with a needlessly hot-headed cameo that brought a yellow card and a separate rebuke from referee Chris Foy.But nothing could take the gloss off United's win as they sealed their place in the last four of the FA Cup.Source: BBC