Barcelona forward Lionel Messi believes the Catalan club's great rivals Real Madrid have improved since Barca beat them to win the Spanish Super Cup in August. “Madrid have strengthened their squad well with the aim of being better this season and they have achieved that,” the Argentine World Player of the Year was quoted as saying in Marca sports daily on Friday. “They have grown since August and they are stronger than last year,” he told the Madrid-based newspaper. “But we are too with the additions we have made.” Jose Mourinho's Real side, who have won nine in a row in La Liga and the Champions League, can stretch their lead over Barca at the top to four points with a win at home to Osasuna on Sunday. Barca, bidding for a fourth straight domestic title, play later on Sunday at Athletic Bilbao.