Barcelona created chances late in the second half Sunday at the San Mames but couldn't beat Bilbao goalkeeper Gorka Iraizoz. Martino also alluded to Messi's absence being a factor with the team's lack of finishing up front.
"We just couldn't find that last pass to help us finish it off," the Argentine coach said. "What is disconcerting is when a team doesn't know what to do, but I didn't see that my team didn't know what to do."
Bilbao struck on the counterattack. The Basque club's stifling pressure high up the field forced Barcelona's defense into hurried passes and giveaways.
Barcelona saw its lead at the top of the standings erased as Atletico Madrid joined it in first place with 40 points. Real Madrid is three points behind.
The Madrid press reveled in Barcelona's struggles, with sports daily Marca writing "Barca Slides; Madrid Thrives" across its front page.
Madrid has been on a stellar run since losing at Barcelona last month. The team is unbeaten in seven games and while Cristiano Ronaldo has been spectacular, Gareth Bale has also stepped up. Bale scored a hat trick in Saturday's 4-1 victory over Valladolid with Ronaldo out injured.
Bale's adaptation to the Spanish league has also put Neymar under watch after the pair arrived in Spain.
Barcelona can at least look forward to a Copa del Rey match against third-tier club Cartagena on Friday as a chance to rebound from a difficult week.
"There's no reason to be alarmed," Barcelona midfielder Sergio Busquets said. "We just need to keep moving forward. We have to win all the games we have remaining until the end of (2013) and to learn from our errors and good things we do."
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