Colon dropped points at home for the second game in a row, as they were held to a scoreless draw by Gimnasia La Plata, but San Lorenzo missed the chance to overhaul the Argentine league leaders as they drew 1-1 with Godoy Cruz.
Those results opened the door for Velez Sarsfield and Jose Oscar Flores' men walked straight through, coming from behind to crush 10-man Belgrano 3-1, with the Primera Division's top goalscorer Mauro Zarate playing a starring role.
The win took Velez to second spot with 13 points, one behind Colon, while they lead San Lorenzo on goal difference.
After Guillermo Farre had given Belgrano a 1-0 half-time lead on Saturday, Velez struck back three minutes into the second half when Zarate burst onto Hector Canteros' well-weighted pass into the right channel and thrashed the ball into the roof of the net from a tight angle.
Zarate had a fine second half and helped put the hosts in front just after the hour-mark, dribbling into the box from the right wing before cutting the ball back for Agustin Allione to score.
Velez scored their third goal on the counter-attack in the 89th minute as Allione linked with Sebastian Dominguez, who found Lucas Pratto on the overlap and the 25-year-old rounded Belgrano's goalkeeper before slotting the ball home.
After a brilliant start to the Torneo Final in Argentina, Colon, who finished last in the Torneo Inicial campaign, have begun to stall as they were outplayed by Gimnasia to notch a second draw in four days.
The visitors had 54 per cent of possession on Saturday and took 12 shots to the six of Colon, who drew 1-1 with Godoy Cruz on Tuesday.
Godoy Cruz came from behind to draw with Colon midweek and had to do the same thing against San Lorenzo on Sunday.
After Godoy Cruz had the better of the first half at home, the visitors took the lead in the 83rd minute through Nicolas Blandi, which would have seen San Lorenzo overhaul Colon in the league table, only for Facundo Castillon to convert a stoppage-time equaliser for the hosts.
The draw kept Godoy Cruz in fifth position in the table with 11 points, one behind fourth-placed Estudiantes, who drew 0-0 with Atletico Rafaela.
With four of the top five drawing, River Plate and Boca Juniors' respective drives up the table continued after wins over Arsenal (1-0) and Racing Club (2-1) respectively.
River (11 points) moved to sixth, while Boca (10) are one position further back in the standings.
On Monday, All Boys overcame Quilmes 2-1 while Tigre scored a late equaliser to draw 1-1 at Rosario Central.
In other results, Olimpo defeated Newell's Old Boys 1-0 and Lanus won 2-0 at Argentinos Juniors.
