Super sub Alexander Sørloth struck again deep in stoppage time to hand Atletico a 2-1 comeback win at Barcelona on saturday, ensuring Atletico will spend La Liga's short winter break on top of the table.
Atletico's 12th straight win in all competitions lifted them three points above Barcelona.
Barcelona have only two wins in their last nine games and could find themselves third on Sunday if Real Madrid beat Sevilla.
Simeone, coaching Atletico since 2011, celebrated winning at Barcelona for the first time.
"We finally did it," Atletico goalkeeper Jan Oblak said. "We are playing well, we started poorly but we knew our chances would come. And in the last minute Sørloth came through. Thanks to him we finally won here. He is the striker we needed."
It was a much more impressive performance from Barcelona, who dominated for long periods and took a deserved lead in the 30th minute.
Pedri started and ended the move, playing a one-two with Gavi, and firing an angled shot into the bottom right corner.
Raphinha almost doubled Barcelona's lead in stunning fashion in the 57th when he lobbed the goalkeeper but the ball came off the crossbar. Robert Lewandowski got to the rebound but sent it onto the head of Axel Witsel, who needed treatment.
Barcelona was made to rue their missed opportunities when Atletico levelled just three minutes later, partly thanks to a defensive blunder.
Barcelona midfielder Marc Casadó tried to clear Julián Álvarez's cross but passed it straight to Rodrigo De Paul, who fired into the bottom right corner. Casadó put his hands to his head and dropped to his knees in dismay.
Worse was to come for Barcelona as, in the sixth minute of stoppage time, Nahuel Molina made a fantastic run to latch onto a through ball and cross in for Sørloth to fire into the back of the net.
It was Sørloth's eighth goal of the season, five of them after he's come off the bench.
Athletic Bilbao came from behind to beat Osasuna 2-1 and extend their unbeaten run to 14 matches and remain just five points behind Atletico.
Gorka Guruzeta and Alex Berenguer sealed the comeback win for fourth-placed Bilbao after Lucas Torro gave Osasuna a 25th-minute lead at El Sadar.
Guruzeta headed Bilbao level in the 31st and Berenguer struck the winner in the 74th.
Mallorca won at Getafe 1-0 and moved up to fifth.
Cyle Larin's 53rd-minute penalty settled the game at Estadio Coliseum to move Mallorca to within 11 points of the top.
The Canada international scored for the third time in his last two games after being brought down in the area by Juan Berrocal. From the spot, Larin fired low and left to beat Getafe goalkeeper David Soria.
Also, Pablo Duran scored twice in the first half to secure a 2-0 win for Celta Vigo against Real Sociedad.
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