Athletic Bilbao ended Barcelona's 10-game winning streak with a superb defensive performance in a scoreless draw Tuesday in the round of 16 of the Copa del Rey.
Although it was the first time Barcelona had failed to score a goal in 22 games, the hosts did extend their unbeaten run to 23 matches.
With star Bilbao striker Fernando Llorente out with a pulled muscle, coach Joaquin Caparros deployed six midfielders and succeeded in smothering Barcelona's attack in the first leg at Camp Nou stadium.
Lionel Messi and David Villa came on for Barcelona as early second-half substitutes but were unable to make an impact.
"It is a shame because we had been playing well," said Pedro Rodriguez, whose team outscored its opponents 42-4 in the 10 victories. "They defended well. It was difficult to find spaces and we lacked precision in our shots. "
Heading into the Christmas break, Barcelona has 21 wins, 2 losses and 4 draws in all competitions and has outscored opponents 77-16.
Guardiola said his team had played many good matches in 2010, "but there are many intense months ahead with games against very strong rivals."
Also Tuesday, second-division team Cordoba drew 1-1 at home against Deportivo La Coruna. Later, Valencia hosts Villarreal in a provincial derby.
The second legs will be played on Jan. 4-5.
Guardiola entrusted Bojan Krkic, who extended his contract by two years to 2015 this week, and Pedro with the starting striker positions.
Bilbao's plan was clear: put 10 men behind the ball and hang on for the return leg at San Mames stadium.
"During these three years we have played against all types of systems," Guardiola said. "We are the ones that have to be able to attack well."
In the first half, Barcelona's attempts were reduced to a pair of rising strikes by Andres Iniesta that drew acrobatic saves from goalkeeper Gorka Iraizoz.
Bilbao midfielder Javi Martinez received a pass from Ander Iturraspe on the half-hour mark, but his weak header was easily saved by goalkeeper Jose Pinto.
The visitors' best chance came when Carlos Gurpegi headed a corner by Markel Susaeta into the side-netting in the 36th minute.
"We were playing against the best team in the world, " Caparros said. "You have to cut all their passing lanes, which is not easy. We ... played well in the middle of the pitch."
Guardiola sent on Messi on in the 54th and Villa replaced an ineffective Bojan the 63rd to try and break the deadlock.
Villa sent a shot wide in the 79th, and two minutes later Messi had a goal disallowed for offside.
Barcelona defender Gerard Pique came close to hitting a late winner, racing forward but shooting just wide of the left post.
"We have to prepare for the second leg because I don't know what Athletic will do," Guardiola said.
Under torrential rainfall at El Arcangel stadium, Ivan Sanchez-Rico scored Deportivo's opener in the 17th from the penalty spot after Cordoba goalkeeper Alberto Garcia had fouled the striker in the area.
Fernando Usero equalized for Cordoba in the 73rd from inside the six-yard box.
On Wednesday, it's: Real Madrid vs. Levante; Atletico Madrid vs. Espanyol; Sevilla vs. Malaga; Almeria vs. Mallorca and Betis vs. Getafe.
