Defending champion Barcelona will be looking to rebound from two straight draws when it hosts undefeated Osasuna in the Spanish league on Saturday.

Twice in the past week, Barcelona coach Pep Guardiola has watched from the sideline as defensive lapses have ruined otherwise strong performances and cost his team victories.

Last week's 2-2 slip at Real Sociedad left Barcelona two points behind leader Real Madrid, and the Catalans can ill afford to lose touch in a season that will most likely be decided between the two powerhouses.

''(We need a) win now, beginning with the game against Osasuna,'' Barcelona midfielder Xavi Hernandez said.

Madrid will try to stay perfect at Levante on Sunday.

While Barcelona continues to dominate possession, its inability to finish off games has exposed holes in its defense.

In Tuesday's Champions League opener, AC Milan striker Alexandre Pato sprinted through Barcelona's makeshift defense of Sergio Busquets and Javier Mascherano to score in the first minute. Barcelona then outplayed the Italians and took the lead, but Thiago Silva headed in the injury-time equalizer.

Barcelona also conceded a similar headed goal to Sociedad last weekend, and Guardiola will surely be looking to tighten his defense against Osasuna's bigger bodies.

''This team is hungry,'' Barcelona defender Carles Puyol said. ''It is normal to talk about these things when you draw two games, but we want to continue making history.''

Guardiola will once again have to patch up a backline with Gerard Pique doubtful as he recovers from a calf injury.

On paper, Osasuna shouldn't provide much of a challenge, but the Pamplona-based team is undefeated and has only conceded one goal in two games. Barcelona's defenders will have to pay special attention to speedy winger Juan ''Nino'' Martinez, who has impressed since joining the club in the offseason.

Barcelona will also miss winger Alexis Sanchez and Andres Iniesta - both out with leg injuries - and need new signing Cesc Fabregas to continue his quick adaptation to his boyhood squad. Luckily for Guardiola, he can also turn to young standout Thiago Alcantara to help Xavi create for its still potent attack.

''They are two important losses because they can break down the defense, Alexis from the flank and Andres through the middle,'' said Xavi, adding that their replacements have the ability to take over where they left off.

''Thiago is an incredible player, he can decide a game,'' Xavi said. ''As far as Cesc, he is from this club and knows the system we use. The most important thing is that everyone understands the way we play, and Cesc does.''

Madrid will look to keep up its good form after winning its Champions League opener at Dinamo Zagreb on Wednesday.

Madrid has outscored its opponents 10-2 in its perfect start to the Spanish league season, and visits a Levante side that has only conceded one goal in two draws so far.

Cristiano Ronaldo has started where he picked up last season when he broke the league scoring record and has already netted four goals.

''We have to keep taking steps forward and not pay attention to what the others are doing,'' Madrid assistant coach Aitor Karanka said. ''Since the preseason we have been playing at the highest level and we must continue in this line.''

On Sunday, Valencia, also with two victories, visits a winless Sporting Gijon with striker Roberto Soldado looking to keep pace with Ronaldo.

After two games without scoring a goal, Atletico Madrid has a good opportunity to finally break through against Racing Santander. And Real Betis will have a tough test as it visits winless Athletic Bilbao without injured striker Ruben Castro, who scored two late winners that have the promoted team at the top of the standings.

Also, it's: Mallorca vs. Malaga; Granada vs. Villarreal; Sevilla vs. Real Sociedad; Getafe vs. Rayo Vallecano; and Zaragoza vs. Espanyol.