The Argentinian broke the deadlock from the penalty spot shortly after the half-hour mark and then scored a header early in the second half to seal the points for Barcelona.
The brace also sees the 27-year-old move ahead of Cristiano Ronaldo in the La Liga scoring charts, totting up 32 goals in 26 starts.
Atletico Madrid were unable to reclaim fourth place after being held to a goalless draw at Espanyol, although Diego Simeone’s side played the entire second half with 10 men.
Atletico were the better side even after defender Miranda was shown a straight red card for an elbow and they were only denied a late winner by some fine goalkeeping by Kiko Casilla.
Although Atletico did well to stay in command of the game after Miranda was dismissed, this was their third straight draw in the league and meant they remained in third place behind Valencia, who beat Deportivo La Coruna on Friday.
Rayo Vallecano took another step towards securing their survival by coming from behind to beat struggling Granada 3-1 at home.
Jhon Cordoba gave the visitors the lead in the eighth minute but after periods of sustained pressure Alberto Bueno levelled for Rayo midway through the second half and 10 minutes later put them ahead, before substitute Adrian Embarba scored a third in stoppage time.
This was a third consecutive home win for Rayo, who move up to 11th position in the table and 10 points ahead of 19th-placed Granada.
In the final game of the night ten-man Athletic Bilbao grabbed a 2-1 win at Celta Vigo, with??Aritz Aduriz on target from the penalty spot in the first half.
Mikel San Jose doubled their advantage before seeing red late on, while Joaquin Larrivey scored a consolation goal for the home side.?? ??