It is the first time Barcelona and Atletico have both been in La Liga’s Champions League qualification spots since August.
Atletico have struggled for solidity and consistency since winning the title last season while Barca are still recovering from a financial crisis and the departure of Lionel Messi.
Yet both teams will be growing in confidence that they can now achieve their minimum objective, which is to avoid missing out on the Champions League next season and the further financial damage that would cause.
Barca are now third, level on points with Atletico in fourth, but having played a game fewer. They might both fancy their chances of finishing second, with stuttering Sevilla only seven points in front.
Atletico’s win over Betis was particularly significant given Betis started the day in third and have looked the mostly likely candidates all season to upset the established top four.
Atletico were ahead after 75 seconds in Seville as Jan Oblak’s punt downfield was flicked onto Angel Correa, who took advantage of some lethargic Betis defending to cross to Felix, the striker given an easy finish.
Betis levelled in the fifth minute of injury-time at the end of the first half after Hector Herrera was robbed of the ball under pressure from Youssouf Sabaly and Cristian Tello guided the loose ball brilliantly into the corner.
Tello was denied by Oblak in the second half while Joaquin almost scored from a corner. Atletico’s Felipe headed against the post before Jose Gimenez failed to bury the rebound.
But Felix struck again on the hour when Marcos Llorente raced in behind and picked out the Portuguese with a cut-back before Thomas Lemar added a third with 10 minutes left, sidefooting in after an electric Antoine Griezmann run down the right to secure victory.