In a clásico in which Lionel Messi and Cristiano Ronaldo did not score for once, the game's biggest moment came from a 19-year-old defender who was included in the side because of injury and suspension. Raphaël Varane, who started in the absence of Sergio Ramos and Pepe, capped a colossal performance with a second-half header that equalised Cesc Fábregas's opener and left the Copa del Rey semi-final poised at 1-1. Barcelona take an away goal; Madrid will feel that they too can get one in the second leg in a month's time.

With ten minutes remaining Varane leapt between Fábregas and Carles Puyol to connect with Mesut Ozil's long looping cross and leave Barcelona ruing the chances that they had missed – and the chances that Varane had denied them. Not least a first half goalline clearance. Madrid too could reflect on the opportunities that had evaded them in a game that always felt open, even when Barcelona began to take a grip in the second period.

"For a 19-year-old, you can't ask for more," said Madrid's assistant manager Aitor Karanka. "He's a kid who is progressing, who's sensible, and we're very happy with him. He was perfect tonight."

Fábregas got the opener just as the clock ticked up to 50 minutes. Messi had swung a pass towards Jordi Alba on the left. Jose Callejón intercepted but his clearance swung back in Messi's direction and he was quickly onto it. Whether loose control or assist, and it looked more like the former, the ball ran through perfectly to Fábregas, one-on-one with Diego López, and he curled the ball hard and low into the far corner.

It was the first time Barcelona had found themselves beyond the Madrid defence after a first half in which they had been effectively blunted, one in which, unusually, there were no goals. And that despite the fact that the first save came from a free-kick conceded after just 47 seconds, Gerard Piqué bringing down Ronaldo. José Manuel Pinto reached backwards to push the Portuguese's shot over.

Madrid had worked the chance as they would often: by pressing Barcelona and robbing, the pitch opening up before them. When Karim Benzema hit the side-netting and much of this arena cheered thinking the ball was in the net, the opportunity had similar origins. Ozil was a constant threat, always available and always bringing clarity to the counters. Even when Barcelona started to move the ball with greater fluidity – a series of slick passes on 12 minutes ushered in a period of keep ball with Andrés Iniesta at its heart – there was still a certain vulnerability about them. And Madrid knew it.

At the other end, Madrid were organised and, above all, fast. Barcelona found few spaces and those that did open quickly closed. Xabi Alonso and Sami Khedira protected the defence, Callejón and Ronaldo backed up the full-backs. Michael Essien outran Messi and twice Varane was swift across the turf from centre to right to suffocate danger. He also cleared one off the line from Xavi after a startling mistake from Ricardo Carvalho, whose weak back-pass gave Fábregas the ball seven or eight yards out.

The second half saw greater opportunities. Ronaldo, stretching, headed a bouncing ball wide from barely three yards and Piqué had to move quickly to clear by the same post soon afterwards. After taking the lead, though, it was Barcelona who created opportunities. Fábregas spun to put one shot over from eight yards, Pedro ran clean through only to dink wide from five yards, and López smothered Messi. When the Argentinian did beat the keeper, he was ruled out for offside – rightly this time.

Then there was Varane. Twice he made perfectly timed interceptions. Fábregas and Messi thought they were through; but as they prepared to shoot, the ball was gone, nicked away by the Frenchman. And when the moment came at the other end, he was decisive again.