The versatile midfielder is on his way back after a five-week spell on the sidelines and could return to action before the end of the season
The Argentina international picked up a knee injury in Barca's 2-2 Champions League draw against Paris Saint-Germain on April 2 and has since been out of action ever since.
Nevertheless, Mascherano is now one step closer to making his comeback after rejoining the rest of the first-team squad in full training, and could be in line to return prior to the end of the season.
Victor Valdes, meanwhile, is still being plagued by a foot injury that kept him out of last weekend's 4-2 win over Betis and could also miss the match at the Vicente Calderon.
Barcelona need just a point to to clinch their 22nd Primera Division title on Sunday when they travel to Atletico.