Adam Federici lay inert on the turf for a moment. He realised the magnitude of what happened. He understood the horror of it instantly. He let his head rest on the grass and closed his eyes as if he was trying to wish it all away, as if he was trying to blot out the din and the agony and the wild celebrations of the Arsenal fans. His face was scrunched against the grass, distorted in a mask of despair. Reading, still struggling to avoid relegation to League One, had performed heroically to push Arsenal into extra-time in this FA Cup semi-final and Federici had pulled off a series of stunning saves to keep the sides level at 1-1 but the Australian goalkeeper guessed there would be no way back now. There had been less than a minute to go before the extra-time interval when Alexis Sanchez had cut in from the left and fired in a stinging shot straight at Federici. He knelt to gather it but somehow it squirmed through his legs and trickled over the line as he scrambled in vain to retrieve it. It was football at its most cruel. In years to come, it will be the enduring image of this game. Alexis Sanchez's low shot squirmed agonisingly through the legs of Reading goalkeeper Adam Federici in extra time . It was a routine shot from Sanchez but the Reading stopper failed to collect it properly in his grasp - an embarrassing gaffe . The ball rolled through his legs and slowly towards the goal line in the 106th minute of the game . Federici tries desperately to stop the ball going over the line after it rolled through his legs and out of his grasp . Reading had fought valiantly but were unable to score another equaliser to take the tie to penalties . Federici lies slumped on the ground as the impact of his error hits him in the FA Cup semi-final against Arsenal . The Reading goalkeeper, who had been magnificent until then, left the field in tears as manager Steve Clarke tries to console him . Federici's opposite number, Wojciech Szczesny (left) of Arsenal comforts his fellow goalkeeper after the game is resolved . Reading: Federici, Gunter, Hector, Pearce, Obita, McCleary, Williams, Chalobah (Cox, 106), Robson-Kanu (Karacan, 90), Mackie, Pogrebnyak (Yakubu, 111). Subs not used: Stephen Kelly, Norwood, Yakubu, Andersen, Cooper. Booked: Chalobah . Goal: McCleary, 54 . Arsenal: Szczesny, Debuchy, Mertesacker (Gabriel, 63), Koscielny, Gibbs, Coquelin (Walcott, 101), Cazorla, Ramsey, Ozil, Sanchez, Welbeck (Giroud, 72). Subs not used: Wilshere, Ospina,  Monreal, Flamini. Goals: Sanchez 39, 106 . When the final whistle confirmed that it would be Arsenal who will face either Liverpool or Aston Villa here at the end of next month, Federici, 30, put his head down and began to walk purposefully from the pitch, his thoughts fixed on some form of escape, some search for sanctuary. The Reading manager, Steve Clarke, tried to console him but he was inconsolable. As he disappeared down the tunnel, he hung his head and wept. Sure, the bigger picture was that Arsenal now have a chance to become the most successful club in the history of this competition by winning it for the second year in succession. The bigger picture is that this time, their success in the FA Cup seems less like a consolation prize and more like a gateway to a new period of glories at a club that had been starved of them until last season’s Cup final victory over Hull. But above all, this was the kind of human drama that peoples this competition and adds to its legend. ‘I am happy we are through,’ said Arsenal goalkeeper Wojciech Szczesny. ‘But I thought Federici was terrific today. He had the game of his life and they only got to extra-time because of him. He was the best player on the pitch. I really feel for him — I have been there, done that.’ Clarke did his best to ease Federici’s pain, too. ‘This is the life of a goalkeeper,’ said the Reading boss. ‘And Adam is a top goalkeeper. There’s every chance he’ll be Reading’s player of the season this year. His performances in the Championship have been crucial. ‘We stick by him. I understand his worth and the supporters understand how important he is. Adam is a strong character as well. He’ll take his disappointment on the chin and on Wednesday night when we play Birmingham I’m sure he’ll be as good as he always is.’ Clarke also complained that refereeing decisions had counted against his team. He had some justification but nothing can dull the memory of how his side pushed Arsenal all the way. There were times when it seemed Arsene Wenger’s team, who had been pegged back by the Championship strugglers in normal time, might be overwhelmed by the sheer relentless refusal of their opponents to accept defeat and by a team spirit that would not fade. The match became a test of Arsenal’s fortitude as well as their class. In former years, they might have buckled. Sanchez leaps skywards to celebrate his second goal of the game for Arsenal against Reading . Sanchez (left) rifles Arsenal into the lead against Reading in the FA Cup semi-final against Reading . Arsenal had an inconsistent first half before Sanchez struck clinically after Mesut Ozil passed to him excellently . Sanchez (third right) turns away in celebration as Reading's players lay crumpled on the ground after conceding . Striker Sanchez (right)  celebrates alongside team-mate Keiran Gibbs after scoring for Arsenal against Reading . Gareth McCleary's second-half strike went over the line for Reading after a deflection from Keiran Gibbs . McCleary runs over to the Reading supporters at Wembley to celebrate scoring the equaliser for the Championship side . Reading's players celebrate the goal with McCleary as they pulled themselves level with Arsenal at Wembley in the semi-final . Arsenal manager Arsene Wenger (centre) gives instructions out to his team before the beginning of extra time . Federici’s mistake gave them an escape route that they followed eagerly. They had nearly taken an early lead when Per Mertesacker rose to meet a corner at the near post and Federici had to dive smartly to his left to push it off the line. Later, he produced a stunning one-handed stop to keep out a header from Gabriel. Reading held firm but Arsenal started to exert more and more pressure. Mesut Ozil, in particular, was a delight to watch in possession. There are increasing signs that the German is finally beginning to find his best form and he beguiled Reading with a series of sweet turns and beautifully measured passes. Seven minutes before the interval, Arsenal broke the stalemate. It was Ozil, inevitably, who was the inspiration. He collected the ball midway inside the Reading half, took time to pick his pass and flighted a curling ball to Sanchez in the box. Sanchez did the rest, although the rest was not simple. He controlled the ball on his chest with his back to goal, turned and committed Garath McCleary by shaping to shoot. Then, with time, the Chilean forward prodded the ball past Federici and wheeled away to celebrate. Gabriel (right), a replacement for Per Mertesacker, powers a header at goal shortly after Reading had scored . But Reading goalkeeper Federici made a splendid one-handed save to tip the ball up and against the crossbar . Sanchez (centre) earlier took the ball past goalkeeper  Federici (second left) before losing his footing and falling . Daniel Williams (left) shoots at goal for Reading against Arsenal at Wembley but his attempt went wide of the goal . It seemed then that Arsenal would extend their lead. Reading’s threat had been negligible. But they came out for the second half with new belief and to the delight of their fans massed behind the goal, they forced an equalizer. Pavel Pogrebnyak must take a lot of the credit for squeezing in a cross when it looked as though he had run out of space near the byline. The ball drifted over Kieran Gibbs’ head and as Szczesny scrambled across his line, McCleary volleyed the ball back across him. Szczesny got his hands to it but he had not been able to prevent it crossing the line. Suddenly, Reading wanted more. Jamie Mackie clipped a lovely chip into the path of Danny Williams on the edge of the box. It fell to him nicely but Williams sliced his volley wildly wide. The game was harum-scarum now. Reading sensed an upset. Mackie urged the fans on and they roared back. But six minutes from the end of normal time, Reading escaped when Aaron Ramsey missed an open goal, crashing a left-foot shot against the post. Ramsey held his head in his hands. Redemption was not far away for him. It will take longer to greet Federici. Arsenal striker Danny Welbeck (centre) has an effort blocked by Reading goalkeeper Adam Federici . Germany defender Mertesacker (left) heads the ball goalwards for Arsenal against Reading . Arsenal attacker  Ozil (left) escapes the attention of Michael Hector (right) of Reading during the semi-final . Laurent Koscielny (centre) leaps up and controls possession as Arsenal took on Reading in the FA Cup semi-final at Wembley . McCleary (left) of Reading takes the ball beyond the challenge of Arsenal player Francois Coquelin . Reading's fans watch on as their Championship side take on Arsenal in the FA Cup semi-final at Wembley on Saturday . Reading manager Clarke gives instructions to his team as they take on Arsenal . Wenger's side failed to hit the level seen in recent games against Reading at Wembley .
Alexis Sanchez scored after 39 minutes following some clever play by Mesut Ozil for Arsenal .
Gareth McCleary's shot was deflected over the line on 54 as Reading hauled themselves level .
Sanchez struck again before half time in extra time when his shot squirmed through Adam Federici's legs .