Malaga claimed a 0-0 draw after successfully nullifying Lionel Messi and Neymar when the two sides met at La Rosaleda in September, and they were just as effective again, producing a determined display to claim their first Camp Nou victory since 1999.
Luis Suarez, who missed their last meeting, was unable to inspire a change in Barca's fortunes this time around, as their usually lethal frontline struggled after Juanmi capitalised on an early Dani Alves error to break the deadlock.
Atletico Madrid started what could be a season-defining run of fixtures with a convincing 3-0 win against Almeria at Vicente Calderon on Saturday.
Mario Mandzukic scored an early penalty before teeing up two first-half goals for strike partner Antoine Griezmann, as Diego Simeone's side cruised past their struggling visitors - although they played the last few minutes with 10 men after Guilherme Siqueira was sent off for a second booking late on.
It was still a welcome win for the champions, who currently sit third behind rivals Real Madrid and Barcelona having lost to Celta Vigo last time out.
Valencia opened up a five-point gap on fifth-placed Sevilla with a hard-fought 2-1 victory at Cordoba.
Nabil Ghilas' second-half penalty had cancelled out Andre Gomes' goal as bottom side Cordoba looked set to earn a point.
But Pablo Piatti proved to be the hero for Valencia with his 81st-minute effort.
Celta Vigo extended their unbeaten league run to four games with a 2-0 victory at Deportivo La Coruna, who finished the clash with 10 men.
