Arch rivals Real Madrid have Cristiano Ronaldo in fine form as the league's top scorer and are unlikely to drop many points between now and the end of the campaign in May.
Barca coach Pep Guardiola, whose side travels to Germany to play Bayer Leverkusen in a Champions League last-16 first leg on Tuesday, spoke of a "painful loss" after the Osasuna match but rejected any talk of throwing in the towel.
"This team never gives up and neither does their coach," the former Barca and Spain midfielder told a news conference.
"We don't really have much room to work with so we can only play the next game as best we can," he added.
Captain Carles Puyol repeated the upbeat message after training on Sunday, saying players were unhappy with their performance at Osasuna but insisting the league was not lost.
"We have to be realistic and acknowledge that it's difficult, but if this team has one thing it's that it never gives up and will fight until the end," Puyol said.
"In the past it was us ahead and we were obliged to win because they [Real Madrid] were chasing us," the Spain centre-back added. "Now we need to try and win to increase the pressure on them."
Barca's patchy performances away from their Nou Camp stadium, with the notable exception of December's 3-1 win over Real at the Bernabeu, have allowed the Madrid club to pull away at the top.
The Catalans have taken only 17 points from a possible 33 on their travels, while at home they have won 10 and drawn one while conceding only three goals to 45 scored. That compares with 18 for and 14 against away.
World Player of the Year Lionel Messi has been unable to consistently reproduce on the road the brilliance he demonstrates at the Nou Camp and just four of his 23 goals this season have come away from home, three of them in a hat-trick at Malaga.
Winger Isaac Cuenca, a promising 20-year-old who has been promoted from the B team to the senior side this season, suggested one reason for the team's away failures is that they sometimes struggle on smaller pitches like the one at Osasuna's Reyno de Navarra as they restrict their flowing passing game.
"It's normal that we are finding it hard away from home," he told reporters on Saturday. "The Nou Camp is bigger and the ball flows more easily."
