A header from Seydou Keita in additional time helped Barca salvage a point in Pep Guardiola's last league game in charge after a Ruben Castro brace put mid-table Betis ahead.

Dani Alves was sent off in the 53rd minute in what proved to be a turning point after Barcelona had looked in control of the encounter.

Sergio Busquets put the visitors ahead when he headed in a curling Xavi corner in the ninth minute, but they squandered several opportunities to double their lead before the interval.

Betis were handed a way back into the contest when Alves inexplicably lunged at Jefferson Montero to pick up his second yellow card of the match.

The home side were buoyed by the sending off and became more aggressive in their search of an equaliser.

Betis piled on the pressure and grabbed their leveller on 71 minutes.

Substitute Roque Santa Cruz flicked the ball into the path of Castro, who chipped his shot over the onrushing Victor Valdes.

Betis turned the game on its head when they took the lead in the 75th minute after a clever passing move.

The neat move saw Castro released behind the Barca defence, and the striker placed his finish past Valdes and into the bottom corner for his 16th goal of the season.

There was to be late drama as Keita managed to get on the end of Martin Montoya's cross in the 92nd minute to send a brilliant header into the far corner as Barca earned a dramatic point.

Third-placed Valencia rounded out their campaign on a low note, suffering a 1-0 reverse at Real Sociedad.

Antoine Griezmann, who scored the winner in the meeting between the teams earlier this season, netted the only goal of the game on 64 minutes as Unai Emery's four-year stint at Valencia finished in defeat.