The Blaugrana were unable to find a way past Inaki Pena, who produced an inspired performance against his parent club in the first leg of the UEFA Europa League Round of 16 at Camp Nou on Friday (AEDT).
Barca had 16 shots, hitting the target four times as it fired a blank to bring an end to a four-match winning run.
The Catalan giant is now unbeaten in nine matches, though, and head coach Xavi is confident his fourth-placed side can fire at home to Osasuna.
He said: "We were very good in Elche [in a 2-1 win last weekend] and they played with a low block.
"We have different solutions but you have to interpret them well in the game. We have trained [well] these days, we have made videos and we try to find solutions.
"We faced a rival who was very good, an extraordinary goalkeeper. I don't see it as a problem."
Xavi says Barca must be relentless as it attempts to maintain its unbeaten run.
"We have to maintain the intensity, they can't beat us in intensity. We can't lower it," he added.
"Being more effective changes the game. The rival has to open up and leave spaces. Getting ahead is an important advantage."
Xavi expects more quality from Barcelona going forward.
"We needed to attack better. We've analysed it. We have to be self-critical. We were better in the second half," he said.
"I don't think beyond it. My mind is not on Thursday's game against Galatasaray. Analysing Osasuna, who do things very well, I focus on tomorrow's game."
