Spanish international Koke rolled home the winner as Atletico Madrid moved three points ahead of Barcelona at the top of La Liga with a 1-0 over Malaga on Saturday.
In a game short on clear-cut opportunities, Koke was in the right place to slot home his fourth goal of the season 20 minutes from time after Willy Caballero had denied Adrian Lopez from close range.
Barcelona can move back to the top with a win over Elche on Sunday before travelling to face Atletico at the Vicente Calderon next weekend.
Real Madrid are now eight points adrift of the leaders, but can also cut the gap when they host Celta Vigo on Monday.
Atletico's Juanfran had the first big chance of the match when he broke into the Malaga box on 21 minutes, but Caballero parried his low drive and the ball rebounded fortunately off Marcos Angeleri away for a corner.
Eliseu was first to threaten for Malaga as he was played in on the right side of the box only for his low effort to be easily held by Thibaut Courtois.
After struggling to breakdown a well-organised Malaga in the first period, Atletico boss Diego Simeone withdrew teenager Oliver Torres for Adrian at the break in an attempt to find the breakthrough.
However, Atletico suffered a setback ahead of Barca's visit just 10 minutes into the second-half when Juanfran was booked for obstructing Victor Antunes and will now be suspended for the Catalans' visit.
Adrian should then have opened the scoring when he was brilliantly played in by Costa, but he delayed in front of goal and allowed Weligton to dispossess him with a fine sliding challenge.
Costa's creation was to prove vital though as he again set-up Adrian inside the area and this time the rebound off Caballero's legs fell kindly for the arriving Koke to slot into an unguarded net.
The goal forced Malaga onto the front foot for the fist time in the match. However, despite a late rally, they failed to seriously test Courtois as Atletico held on for another vital three points in the title race.
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