Pablo Machin’s side are unbeaten in seven league games since a 4-2 loss at Barca, who play Levante later on Sunday, in October.
The hosts had to wait until the 55th minute to break the deadlock, when striker Andre Silva was tripped in the area by Girona defender Juanpe.
Argentinian Banega stepped up to send visiting goalkeeper Gorka Iraizoz the wrong way from the penalty spot.
The points were wrapped up only nine minutes later, as Wissam Ben Yedder cut the ball back for the onrushing Sarabia to slide home his 14th goal of the season in all competitions.
On Saturday, Atletico Madrid had also drawn level on points with Barcelona as Antoine Griezmann’s 80th-minute strike grabbed a 3-2 victory at Real Valladolid, while Real Madrid sit just two points adrift after edging out Rayo Vallecano 1-0.