كتب : وكالات
Ronaldinho put the Catalan giants ahead after six minutes from the penalty spot after Deco was tripped by Betis defender Melli Andreu.
Barcelona squandered a couple of chances to double the lead in the first-half through Samuel Eto'o and Andres Iniesta.
The hosts' attacking display was largely affected by Frank Rijkaard's decision to substitute Ronaldinho and Lionel Messi in the 67th and 75th minutes respectively.
Sobis stunned the home crowd shortly before the end when a quick-taken free-kick by Assuncao released him inside the area before firing a shot at the near post past Barca keeper Victor Valdes.
Real Madrid, who beat Espanyol 4-3 on Saturday, have become on top of the league table with 66 points, on level with Barcelona but Los Meringues have the head-to-head advantage.