Atletico Madrid coach Diego Simeone ran down the touchline in joy while Barcelona players sunk to the turf in dismay.
Super sub Alexander Srloth struck again deep in stoppage time to hand Atletico a 2-1 comeback win at Barcelona and ensure Atletico will spend La Liga's short winter break on top of the table.
Atletico's 12th straight win in all competitions lifted it three points above Barcelona.
Barcelona has only two wins in its last nine games and could find itself third on Sunday if Real Madrid beats 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 Srloth came through. Thanks to him we finally won here. He is the striker we needed.
It was a much more impressive performance from Barcelona, which dominated for long periods and took a deserved lead in the 30th minute.
Pedri sta