BARCELONA, Oct 24 (Reuters) - Real Madrid beat Barcelona 2-1 in the first Clasico of the season in front of 86,422 fans at the Camp Nou on Sunday after a sensational strike from defender David Alaba and a late goal from Lucas Vazquez gave Carlo Ancelotti"s side three points. Victory was Real"s fourth straight in Clasicos and also Ancelotti"s first at the Camp Nou in six visits, with his side devastating on the counter-attack and the result moving them provisionally top of LaLiga with 20 points. "We played a practical game. We knew what we need to do and the boys executed the game plan perfectly," Ancelotti said. "Our team enjoy playing on the counter-attack and I have to take advantage of that." Barcelona controlled possession in the first half but Real took the lead when Alaba started a flowing move with a tackle and finished it at the other end with a left-footed drive from the edge of the box. Barcelona manager Ronald Koeman brought on Philippe Coutinho at halftime while strikers Sergio Aguero and Luuk de Jong were also thrown on in the second half as they searched for an equaliser. With seven minutes of injury time added on, Real doubled their lead when Marc-Andre ter Stegen saved a shot from Marco Asensio from another counter-attack but Vazquez was quicker than Gerard Pique to pounce on the rebound to score. The home side got a goal back in the 97th minute when Sergino Dest crossed to the Aguero in the six-yard box and the Argentine tapped in for his first goal in a Barcelona shirt. But it proved to be a consolation goal, leaving Barcelona five points behind in eighth place. REAL"S SPEED ON THE COUNTER Koeman had warned his players they needed to be more effective when controlling the ball possession and that stopping Real"s speed on the counter would be decisive but that was easier said than done. Barca managed to get the ball into dangerous positions around Real"s box but they lacked the final pass. At the other end, Vinicius Jr"s speed and power on the counter-attack left Barca"s defence scrambling time after time. The Brazilian was on fire and almost scored twice in the span of five minutes. He first dribbled past two players and fell inside the area after contact with Jordi Alba but he was denied a penalty while he was also denied another opportunity when the linesman signalled offside with Ter-Stegen beaten. Barcelona wasted their biggest opportunity of the first half when Memphis Depay led a counter-attack and crossed to Dest, who was unmarked in the box but he volleyed the ball into the stands. "I"m not happy with the result. I think we deserved more," Koeman said. "We knew that we couldn"t afford to miss opportunities and that if they got the lead, they know how to defend. We were not good in the last quarter (of the pitch). "Losing at home to our biggest rivals in a close game is though to swallow." Coutinho gave new life to Barca when he came on for Oscar Mingueza but Real kept persisting with the long balls to Vinicius, who left the game exhausted late on for Asensio.