Manchester United sealed a place in the Champions League semi-finals with victory over Chelsea as Carlo Ancelotti's decision to axe Didier Drogba in favour of Fernando Torres backfired at Old Trafford.Ancelotti took the gamble of favouring the British record £50m capture from Liverpool ahead of Drogba in an attempt to overhaul the one-goal advantage United were protecting from the first leg at Stamford Bridge.The striker's struggles continued, however, and he was hauled off at half-time after Javier Hernandez doubled United's lead in the tie moments before the break.Drogba underlined the error of his coach's ways with an outstanding second-half show that even brought Chelsea hope when he scored with 13 minutes left as Ancelotti's side struggled under the handicap of being reduced to 10 men when Ramires was sent off for a second yellow card after fouling Nani.If Chelsea harboured any ambition of turning the game on its head, it was short-lived as Park Ji-sung restored United's lead seconds later to clinch a meeting with either holders Inter Milan or Schalke 04 in the last four.As Old Trafford celebrated at the final whistle, Ancelotti cut a predictably disconsolate figure with only the very faint prospect of challenging United for the title left in his attempts to follow up the Premier League and FA Cup Double he claimed in his first season.And while his decision to go with Torres ahead of Drogba showed commendable courage, as did his decision to take the Spaniard off after only 45 minutes, he now faces the prospect of the selection potentially starting the credits rolling on his Chelsea career following the exit from the tournament owner Roman Abramovich is desperate to claim.If Torres is looking an expensive misfit at £50m, United's swoop for Hernandez can already be regarded as one of the great bargains with another prime example of the goal-poaching instincts that came with only a £6m price tag attached.United can now turn their attentions to Saturday's FA Cup semi-final against neighbours Manchester City at Wembley as their charge for a repeat of their 1999 Treble remains firmly on course.Ancelotti made the big call in selecting Torres ahead of Drogba and the early signs looked good for Chelsea as they took the game to United with ambition and purpose in pursuit of the goal they required.Chelsea created early opportunities but crucially, given the balance of the tie, they were wasted. Nicolas Anelka was twice narrowly off target and Frank Lampard should have done better than shoot straight at Edwin van der Sar following good work by Florent Malouda.Wayne Rooney and Hernandez have developed a potent partnership and they almost created the breakthrough for United when the Mexican headed in an inviting cross, only to be ruled offside by the slenderest of margins.United keeper Van der Sar made light of his 40 years with a sprightly dash from goal to make a perfectly timed tackle and clearance on Anelka as the Chelsea striker escaped the attentions of his markers.As Chelsea neared the end of a first half they would have regarded with a measure of satisfaction, United struck a devastating blow that underlined the importance of those missed chances.John O'Shea fashioned the original opening with a perfect pass inside Anelka and Giggs was equally incisive with a cross that was bundled into the roof of the net in trademark fashion by the predatory Hernandez.Ancelotti needed to act and his response was dramatic by any standards, hauling off Torres and replacing him with Drogba in an attempt to rescue a quarter-final that was slipping away.And Drogba wasted no time in making more of an impression that the struggling Spaniard, firing in an effort that left Van der Sar scrambling and a free-kick that the keeper was forced to punch to safety.Chelsea's efforts to somehow snatch at a lifeline suffered a setback with 20 minutes left when Ramires flew into a reckless tackle on Nani and left referee Oligario Benquerenca with no option other that to brandish a second yellow card.Drogba then gave Chelsea hope, if only for a matter of seconds, when he took Michael Essien's pass on his chest and drilled a low finish beyond Van der Sar.If Chelsea had thoughts of completing an unlikely fightback, they were snuffed out almost immediately as another Giggs cross found Park unmarked on the angle of the penalty area, the South Korean making the most of the time and space afforded to him to beat Petr Cech.United ran down the clock with comfort - now time may also be running out for Ancelotti.Source: BBC