Barcelona crushed Real Valladolid 3-0 away to move eight points clear at the top of La Liga Saturday, reaching the mid-point of the season unbeaten for the first time. Xavi Hernandez and Daniel Alves scored for the defending champion in the first half and Lionel Messi added the third as Barcelona comfortably won its third game in a row - having outscored opponents 12-0 during that span. Alves was behind many of Barcelona's best attacks down the right flank and sent a perfect cross into the area that found the unmarked Xavi, who volleyed in the opening goal in the 20th minute. Two minutes later, Alves was played clear down the right and curled a right-footed shot from outside the area over goalkeeper Justo Villar inside the far post. Messi then scored his league-leading 15th goal in the 56 after a pass from Zlatan Ibrahimovic. It was Barcelona's first game since coach Pep Guardiola agreed to a one-year contract extension. Barcelona has won 15 games and drawn four for 49 points. Madrid has 41, Valencia is on 38 while Sevilla joined Mallorca with 33 points following a 1-0 win over Almeria earlier Saturday. Athletic, Espanyol, Madrid and Real Sociedad also finished the first half of the season unbeaten. It was Barcelona's second highest point total after 19 games - one less than the Spanish champions had at the same point last year. Sevilla beat Almeria with an Alvaro Negredo goal after some quick thinking on a waterlogged pitch at the Sanchez Pizjuan. Heavy rain during the day made life difficult for both sides at first, with the ball regularly being held up in puddles, and forced an error from the visitors after 10 minutes. Santiago Acasiete's backpass to his goalkeeper ran up short in the area and Renato nipped in and squared for Negredo to score in the empty net. But Sevilla had to endure a nervy 80 minutes before securing the points to end a run of four straight league defeats. Roma beats 10-man Juve In Milan, John Arne Riise scored an injury-time winner to give AS Roma a 2-1 win over Juventus Saturday after goalkeeper Gianluigi Buffon was sent off in the 83rd minute. Alessandro del Piero had given Juventus the lead in the 51st minute, before Francesco Totti equalized with a penalty in the 68th. Buffon was then given a red card for a professional foul on Riise outside the area when he was through on goal, and the Norway defender took advantage by heading home David Pizarro's cross in injury time. The win leaves Roma in third place with 38 points, while Juventus stays fifth with 33. In the other match Saturday, Catania beat Parma 3-0 after goals from Giuseppe Mascara, Jorge Martinez and Takayuki Morimoto. Despite the win, Catania remained in the relegation zone.