In-form attacker Lucas Pratto was on target again as Velez made it four wins from four, edging Lanus 1-0 at the Estadio Jose Amalfitani on Thursday.
Pratto, who netted a brace against Independiente on Saturday, scored his fourth goal in three games with a strike seven minutes from time in Buenos Aires.
Velez are two points clear of River Plate at the league summit after four matchdays.
River Plate have dropped points previously but remain unbeaten following Wednesday's comfortable 3-0 victory over Defensa y Justicia.
Marcelo Gallardo's River drew their opening game but won back-to-back games prior to Defensa's arrival at the Estadio Monumental Antonio Vespucio Liberti.
And the Argentine powerhouses extended their winning streak courtesy of Carlos Sanchez's first-half double.
Sanchez got the ball rolling in the 34th minute, winning possession inside the halfway line and initiating an attacking move before heading home a Leonardo Pisculichi cross.
The Uruguayan midfielder was at it again two minutes shy of the half-time break, using his head for a second time to convert a rebound.
Colombian forward Teofilo Gutierrez sealed the points with 13 minutes remaining, directing a header into the top corner after Defensa's defence failed to cope with a ball across the six-yard box.
Racing Club, Newell's Old Boys, Godoy Cruz and Estudiantes also returned to winning ways.
Former Inter striker Diego Milito netted an 87th-minute penalty as third-placed Racing Club - three points behind Velez - edged Arsenal 1-0 on Tuesday.
Newell's Old Boys - fourth in the standings - almost squandered a three-goal lead but survived to win 3-2 at Atletico Rafaela on Wednesday.
Argentina international Maximiliano Rodriguez, Leandro Fernandez and Adrian Bastia's own goal helped Newell's to a comfortable first-half lead.
But Atletico Rafaela insured a nervy finish thanks to late goals from Joel Sacks and Sergio Vittor.
Fifth-placed Godoy Cruz got the better of rivals Rosario Central on Wednesday thanks to Ruben Ramirez's 69th-minute goal.
Both teams ended the match with 10 men following red cards to Sebastian Abreu (Rosario) and Luis Jerez (Godoy Cruz).
As for Estudiantes, they heaped the pressure on Boca Juniors after triumphing 3-1 on Wednesday.
Estudiantes eased past struggling Boca, who are fourth from bottom, courtesy of Diego Vera's first-half brace and Joaquin Correa's opener.
Copa Libertadores champions San Lorenzo claimed their first points of the season, climbing off the foot of the table with a 3-0 win at Quilmes on Thursday.
First-half goals from Hector Villalba and Gonzalo Veron, and Nestor Ortigoza's stoppage-time penalty saw San Lorenzo to victory in Buenos Aires.
In other results, Sebastian Penco and Federico Mancuello both struck in the final two minutes as Independiente upstaged 10-man Olimpo 2-1 on Tuesday.
Second-bottom Belgrano and Gimnasia La Plata were also in action on Tuesday, playing out a goalless draw.
Meanwhile, Banfield accounted for Tigre 1-0 on Thursday.
