By Iain Rogers
MADRID (Reuters) - Lionel Messi smashed in a superb free kick to complete a 2-1 comeback win for injury-hit Barcelona at home to Athletic Bilbao on Sunday that kept alive their slim hopes of a fifth La Liga title in six years.
After a wretched 12 days when they were eliminated from the Champions League by Atletico Madrid, beaten in the King's Cup final by Real Madrid and suffered a shock 1-0 reverse at lowly Granada in La Liga, Barca badly needed a morale-boosting victory in front of their fans at the Nou Camp.
However, after Messi, Pedro and Alexis Sanchez squandered clear scoring opportunities, Aritz Aduriz fired fourth-placed Bilbao ahead five minutes into the second half, prompting rumblings of discontent among the home faithful.
Pedro leveled in the 72nd minute after more chances had gone begging and Messi struck the winner three minutes later when he drove the ball powerfully into the net, the Argentina forward's 26th goal of an injury-disrupted season.
With four matches left including a trip to Barca on the final day of the season, surprise leaders Atletico top the standings on 85 points following Friday's 2-0 home win over Elche.
Barca are second on 81 points, two ahead of Real, who have a game in hand. Bilbao are a further 17 points behind Real and remain well placed to secure a berth in Champions League qualifying for next season.
"We are creating a lot of chances but finding it tough to put them away," Barca center back Javier Mascherano said in an interview with Spanish television broadaster Canal Plus.
"We just have to do things as professionally as possible for the remaining few games," added the Argentine, who made a superb block late on to deny Bilbao substitute Mikel Rico.
"We have to hold on to this small amount of hope we have, try to win all our matches and see what happens."
Barca have been ravaged by injuries in recent weeks and were without Brazil forward Neymar and the Spain trio of left back Jordi Alba, central defender Gerard Pique and goalkeeper Victor Valdes for Bilbao's visit.
They lost to the Basque club at the San Mames in December and looked hungry for an early goal in the return, Messi and Pedro drawing fine saves from goalkeeper Gorka Iraizoz before Adriano had a shot cleared off the line by Mikel Balenziaga.
In an entertaining contest featuring two attack-minded sides, Aduriz cracked a stunning overhead kick against the post on the half hour and Alexis scuffed a shot against the crossbar two minutes later when it seemed easier to score.
Five minutes into the second half Bilbao were ahead. An error from Barca center back Marc Bartra surrendered possession in a dangerous position and Aduriz strode forward before firing clinically past keeper Jose Manuel Pinto.
Barca had two chances to level but both were wasted. Pedro fired straight at Iraizoz when well placed inside the area in the 58th and Messi sent a shot narrowly wide of the post when clean through two minutes later.
Good work down the right from Dani Alves led to Barca's equalizer. The Brazil fullback squared for Alexis and his cross-shot was turned into the net by Pedro before Messi's fierce free kick was too hot to handle for Iraizoz.
"It's a shame because we had our chances to win but now we need to move on and focus on the next match," the Bilbao keeper told Canal Plus.
"We cannot take our foot off the gas now and we have to keep up the effort so we can achieve our objective" of securing fourth place, he added.
Bilbao are three points clear of fifth-placed Sevilla, who continued their fine recent run with a 4-0 victory at home to Andalusian rivals Granada on Sunday.
Celta Vigo pulled further away from danger when they won 4-2 at second-from-bottom Almeria, while basement side Real Betis are on the brink of relegation after they were beaten 3-1 at Rayo Vallecano.
(Editing by Ed Osmond)