Real Madrid's defenders have not been performing as well as they should in pre-season and need to lift their game for the coming campaign, according to centre-back Ricardo Carvalho.
"We know we have to improve and we are working on it," the Portuguese was quoted as saying in Friday's edition of sports daily Marca.
"It's not normal that we are letting in so many goals and we have to work better as a team," the former Chelsea player added.
Jose Mourinho's side begin their quest to deny Barcelona a club record-equalling fourth straight domestic at Real Zaragoza on Sunday.
Barca take on Porto in the European Super Cup in Monaco later on Friday before hosting Villarreal in the Monday La Liga match when new signing Cesc Fabregas could make his home league debut after returning to his boyhood club from Arsenal.
Villarreal may still be reeling after being drawn in a tough-looking Champions League group with Bayern Munich, Manchester City and Napoli but left-back Joan Oriol is confident they can challenge Barca at the Nou Camp on Monday.
"We'll try to use our weapons, pressuring them high up the pitch and trying to get the ball off them," Oriol, whose brother Edu played for Barca's B team before joining Zaragoza.
"We have always played really good matches against Barca and we'll try to do so again," he told a news conference.
Real have been playing up the goal-scoring exploits of forward Cristiano Ronaldo in the build-up to the start of the season, noting on Friday that his 40 goals last term equalled a record held by former Bayern Munich striker Gerd Muller.
German international Muller netted 40 in the 1971/72 campaign, a record for Europe's top five leagues. Ronaldo's 40 last season was the most ever in La Liga, beating a previous best mark of 38 jointly held by Zarra and Hugo Sanchez.
Valencia, third last term, may still dip into the transfer market before the window closes at the end of the month after bringing in players that include midfielders Sergio Canales and Dani Parejo, coach Unai Emery said on Friday.
"Valencia has the option until August 31 and we have to be ready in case we can improve things," Emery told a news conference, adding that the club were not only interested in another defender.
Big-spending Malaga start their campaign on Sunday at Sevilla after a summer spending spree that brought players including Dutch striker Ruud van Nistelrooy, Spain midfielder Santi Cazorla and Valencia winger Joaquin to the Qatari-owned Andalusian club.
Coach Manuel Pellegrini wants his side, which narrowly avoided relegation last term, to qualify for Europe next season and is also eyeing a strong performance in the King's Cup.
"We have a very good squad and it's up to the players to show
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