MADRID (AFP) Reigning European and Spanish champions Barcelona will aim to put their first dip in form of the season behind them when they host Real Zaragoza in La Liga on Sunday. After losing their perfect league record with a 0-0 draw at Valencia, the Catalan side suffered a shock 2-1 Champions League home defeat by relatively unknown Russians Rubin Kazan in mid-week. The Kazan loss was Barcas first since the end of May when they lost 1-0 at home to Osasuna having already wrapped up the league title. I dont believe in positive defeats, nor that it gives us a reality check, said coach Pep Guardiola, whose side lead Real Madrid by a point. Real also lost at home in Europe with a 3-2 reverse against AC Milan but have the chance to go above Barcelona as they are in action first on Saturday at Sporting Gijon. Atletico Madrid harboured aspirations to challenge Barca and Real for the title but hover a point above the relegation zone with their coach Abel Resino clinging to his job after a 4-0 mauling by Chelsea in the Champions League. I am not worried about my situation but the teams situation, explained Resino. Former Getafe coach and Real Madrid favourite Michael Laudrup has been identified as Resinos likely successor in the Spanish media. Atletico host high-flying Real Mallorca, currently fifth, at the Vicente Calderon on Saturday aiming to tighten up at the back after leaking eight goals in their last two matches. Barcelona, in contrast, have the best defence in the league but must do without Brazilian defender Dani Alves, who is out for three weeks with a thigh injury sustained against Rubin, so Carles Puyol may deputise at right-back. Lionel Messi may be the favourite to win the Ballon dOr but he has received criticism following some below-par displays for Argentina and Barcelona. He is so strong mentally, said Guardiola. He is the best player in the world and will continue to show that. Real are still waiting for their Messi equivalent, Cristiano Ronaldo, to return from an ankle injury so will turn to Brazilian Kaka for inspiration in Gijon on Saturday. Going forward Real have been menacing but at the back they look unsure and even the ever-reliable goalkeeper Iker Casillas is having problems and was at fault for two of Milans goals in the 3-2 Champions League defeat. Madrid have leaked seven goals in their last three matches and Spanish international centre-back Raul Albiol called for an improvement. We have to learn from our mistakes, said Albiol. If we cant win games we at least have to learn not lose them. While the trio of Barcelona, Real and Atletico Madrid all lost in Europe, Sevilla made it a perfect three wins with a 3-1 triumph at Stuttgart to top their Champions League group. Sevilla entertain Espanyol on Saturday hoping to bounce back from a 1-0 loss at Deportivo La Coruna last time out. Real arent at the same level as at the start of the season and Barcelona have dipped, said Sevillas Aldo Duscher. This is added motivation for us to try and catch up and perhaps go past them. Villarreal were expected to be tussling with the top sides but are the only side without a win and prop up the standings going into Sundays home match with Malaga. It has been a nightmare start for coach Ernesto Valverde, who has not won a league match since taking charge. Malaga were challenging for the Champions League last season but have lost five out of their opening seven games to lie second from bottom, a point in front of Villarreal. Fixtures Saturday Atletico Madrid v Real Mallorca (1600GMT), Sporting Gijon v Real Madrid (1800GMT), Sevilla v Espanyol (2000GMT) Sunday (1500GMT unless otherwise stated) Valladolid v Deportivo La Coruna, Getafe v Athletic Bilbao, Tenerife v Xerez, Racing Santander v Osasuna, Almeria v Valencia (1700GMT), Barcelona v Real Zaragoza (1900GMT)