Increasingly error-prone David de Gea was at fault twice as Chelsea ended Manchester United's long unbeaten run with a 3-1 win at Wembley to book their place in the FA Cup final against Arsenal
The United keeper is under pressure after a series of uncharacteristic mistakes this season, and there was no way back for his team on Sunday after his poor attempts to keep out shots from Olivier Giroud (45+11) and Mason Mount (46) either side of half-time
Chelsea were handed a third when Maguire (74) diverted a cross past De Gea at his near post and, although Bruno Fernandes (85) converted United's 19th penalty of the season, it was nothing more than a consolation as the Blues - who had lost their three previous matches with United this season - cruised into the final, which takes place on August 1
De Gea's latest performance will fuel debate for the coming months over his status as undisputed No 1 but more immediately United - who hadn't lost in 19 - must now bounce back from the disappointment to try to secure a top-four finish before turning their attentions to the Europa League
 Chelsea, meanwhile, can now look forward to competing for a ninth FA Cup - and adding to the four boss Frank Lampard picked up as a player
Both teams switched to three-man defences for the tie and it led to a cagey opening period
 De Gea punched away a swerving Reece James shot from distance and Marcos Alonso headed wastefully over before Fernandes' clipped free-kick was tipped behind by Willy Caballero but chances were at a premium
Kurt Zouma went close on 39 minutes, clashing heads with Eric Bailly in the process, before Bailly was again on the deck moments later when his captain Maguire headed the back of his head
 It was a painful collision, leaving Maguire with a bandage, Bailly forced off injured and over 11 minutes of injury time added to the half
Ole Gunnar Solskjaer sent Anthony Martial on in Bailly's place, shifting to a 4-3-3 formation, and the French striker was immediately into the action, running onto a long ball before being taken down by Zouma as he cleared the ball on the edge of the box
Ref Mike Dean didn't award a foul despite United's strong claims and just a couple of minutes later Chelsea were ahead
 Giroud met Cesar Azpilicueta's cross and, from five yards out, squeezed the ball in off De Gea to give the Blues the advantage at the break
That lead was doubled less than a minute after the restart when Mount found some space, drove forwards and drilled a low shot at goal
 It shouldn't have troubled a keeper of De Gea's calibre but the Spaniard parried the ball into his own net and the shocked reaction of Maguire and Brandon Williams in front of him underlined just how badly he had got it wrong
Marcus Rashford fired a shot across goal narrowly wide and Maguire headed at Caballero as United sought a response but Chelsea remained dangerous on the counter with Mount shooting over from 15 yards
 And it was Chelsea who crucially struck next, when Maguire prodded past De Gea as he tried to keep Antonio Rudiger from doing the same from Marcos Alonso's low cross
United eventually got on the scoresheet themselves with five minutes to play - Fernandes stylishly tucking in after Callum Hudson-Odoi had clipped Martial but it came far too late for a dramatic turn around
 De Gea's errors - which add to his mistakes against Watford, Everton, Tottenham and Bournemouth this season - had already left United too much to do, while Chelsea can now dream of a return trip to Wembley
Manchester United have both taken (19) and scored (15) more penalties than any other Premier League side this season in all competitions
Manchester United host West Ham on Wednesday, live on Sky Sports Premier League, kick-off 6pm
Chelsea travel to Liverpool live on Sky Sports Premier League on Wednesday, kick-off 8
15pm
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>
<PAD>