A goal in each half from Ignacio Piatti led the way for San Lorenzo as the club notched a 3-0 win over Gimnasia to remain within one point of first-place Newell's.
Piatti opened the scoring in the 12th minute before Pablo Alvarado doubled the lead early in the second half for the home side.
Seven minutes later Piatti made it 3-0 to secure the win, giving San Lorenzo 13 points from a possible 15 in the club's last five matches.
Newell's remains one point clear after a 2-0 home win over Argentinos Juniors as Maxi Rodriguez and Pablo Perez found the net for the leaders.
Arsenal stayed in third thanks to Ramiro Carrera's 53rd-minute goal in a 1-0 win over Godoy Cruz, which finished the match with nine men, All Boys managed a 1-1 draw against Rosario Central despite playing the final 58 minutes with 10 men, while Estudiantes and Velez Sarsfield battled to a 0-0 draw in a clash of mid-table sides.
Olimpo lost for the fifth time in nine games after dropping a 2-0 decision at Atletico Rafaela and Tigre secured a 1-0 home win over Colon, which had three players sent off in the second half.
Boca Juniors sits in fourth place after a brace from Emmanuel Gigliotti helped the side to a 2-0 win over Quilmes, keeping Boca two points clear of rivals River Plate, which got a goal in the 89th minute from Gabriel Mercado to beat Lanus, 1-0.
Belgrano piled more misery on last-place Racing in Sunday's other match as Cesar Pereyra scored twice in a 3-0 Belgrano victory, leaving Racing with seven defeats from its first nine games.