Atletico stay top, Messi penalty edges Catalan derby
Atletico Madrid's forward Diego Costa (L) celebrates a goal with teammate Filipe Luis during a Spanish league football match against Athletic Bilbao at the San Mames stadium in Bilbao on March 29, 2014 - by Rafa Rivas
Barcelona had earlier rounded off a fine week by overcoming stiff resistance from local rivals Espanyol to win 1-0 thanks to a late Lionel Messi penalty.
Atletico got off to the worst possible start as Iker Muniain lobbed home the opener after just six minutes, but Diego Costa levelled midway through the first-half.
Koke then grabbed the winner 10 minutes into the second period before Athletic's Aymeric Laporte was sent off late on for a second bookable offence.
Barcelona were also made to work for the three points as Messi scored the only goal from the spot 14 minutes from time after Javi Lopez was adjudged to have handled inside the area.
Espanyol were then reduced to 10 men when goalkeeper Kiko Casilla saw a straight red card for blocking Messi's goalbound effort with his hands outside the area.
Victory for the leaders means that Atletico still lead Barca by a point with seven games remaining, whilst Real Madrid are now six points adrift of Atletico but can cut the gap with victory over Rayo Vallecano later on Saturday.
"Derbies are always the same and you have to win them," said a relieved Barca boss Gerardo Martino.
"It doesn't come easy and they are always tight games, for that reason this was a risky away game for us and we value the three points even more."
Barca now firmly have the destiny of the title in their own hands as they host Atletico on the final day of the season.
However, the Argentine is taking nothing for granted after suffering a shock defeat to relegation threatened Valladolid earlier this month.
"What is left continues to be very difficult and very important. We still have seven finals left between now and the end of the league season and in those games we will also have with us the memory of our defeat in Valladolid."
It looked as if Barca would end the day back on top of the table early in on Bilbao as Aritz Aduriz cushioned a long ball into Muniain's path and he sent a perfectly weighted lob over Thibaut Courtois and just under the crossbar.
Costa had a chance to reply almost immediately as he was played in by Koke, but his shot was too close to Gorka Iraizoz and the keeper parried the ball to safety.
The Spanish international made amends with a similar chance nine minutes later when he was again sent through on goal by Koke and this time finished low into the far corner for his 33rd goal of the season.
Raul Garcia had a great chance to put Atletico in front moments later when he blazed Filipe Luis' low cross well over the bar.
However, the hosts could also have been back in front before the break when Markel Susaeta headed inches wide at the end of a similar move from the one with which Athletic opened the scoring.
Costa was left cursing his luck twice in quick succession at the start of the second period as he raced onto another long ball and shot inches wide before being clearly tripped by Laporte inside the area, but the referee waved away his penalty claims.
Oscar de Marcos should then have restored Athletic's lead when he fired wastefully over after robbing possession from Diego Godin.
However, instead it was Atletico who got the vital third goal as Costa fed Luis on the left and his cross was headed home at close range by Koke.
Courtois was forced into one brilliant save from a towering header by Aduriz as Athletic pressed for an equaliser.
But they couldn't find a way through and Athletic finished the game with 10 men as Laporte saw a second yellow card for chopping down Costa five minutes from time.