Real Madrid moved provisionally to the top of La Liga table on Saturday after Karim Benzema's flicked finish helped them claim a thrilling 2-1 victory over Barcelona in a wild El Clasico at Valdebebas.
Benzema's superb piece of skill and a deflected Toni Kroos free-kick put Madrid in charge and while Oscar Mingueza pulled one back for Barca, they fell to defeat in what could be Lionel Messi's final appearance in this fixture.
Victory means Real Madrid go level on points with Atletico, with the top three now separated by a single point.
Atletico, without the injured Luis Suarez, face Real Betis on Sunday.
But Real Madrid now own the better head-to-head against both of their rivals while Barcelona and Atletico still have to play each other at Camp Nou in the run-in.
With Atletico stumbling and both Barca and Real Madrid hitting their stride, this game looked set to define, if not the title, then who would become favourites to be crowned champions in May.
The result was a riveting contest at a rain-soaked Alfredo di Stefano stadium - certainly, one of the most exciting Clasicos in years - that saw both teams squander numerous chances, several efforts come back off the woodwork and Casemiro sent off in extra time.
With the last play of the game, Barcelona substitute Ilaix Moriba rattled Real Madrid's crossbar.
"We're still in it," said Barca coach Ronald Koeman.
"We've lost a game against a team who is also fighting for the league but we have eight-game left and we will fight to the end."
Casemiro's red card had also given Messi a free-kick and the chance for a dramatic equaliser but instead, the Argentinian made it seven games now without a goal against Real Madrid, with many wondering if his 45th Clasico will be his last.
Messi might yet turn the tide in the eight games still remaining but there is no doubt Madrid are in the groove after backing up beating Liverpool 3-1 on Tuesday with another crucial victory.
They can finish the job in the Champions League at Anfield next week although Zinedine Zidane admitted afterwards his players are "physically at their limit".
"It was a difficult game, the first half was ours, but we suffered in the second," said Zidane. "We deserved the victory, because we had a lot of chances to score the third."