Due to issues regarding his legal status in the Royal Spanish Football Federation, Messi missed the start of La Liga, but on 26 September, he acquired Spanish citizenship and became eligible to play. Wearing the number 19 shirt, he gradually established himself as the first-choice right winger, forming an attacking trio with Ronaldinho and striker Samuel Eto'o. He was in the starting line-up in major matches like his first "Clásico" against rivals Real Madrid on 19 November, as well as Barcelona's away victory over Chelsea in the last 16 round of the Champions League, which came on back of an intense period of rivalry between the clubs leading a resentful Messi to state, "We would rather play Arsenal, Manchester United or anyone else than be on the pitch with Chelsea." After he had scored 8 goals in 25 games, including his first in the Champions League, in a 5–0 win over Panathinaikos on 2 November 2005, his season ended prematurely during the return leg against Chelsea on 7 March 2006, when he suffered a torn hamstring. Messi worked to regain fitness in time for the Champions League final, but on 17 May, the day of the final, he was eventually ruled out. He was so disappointed that he did not celebrate his team's victory over Arsenal in Paris, something he later came to regret.