League-leading River made it seven wins from 11 matches with a 1-0 victory at Newell's on Sunday.
Ramiro Funes Mori - back from serving a one-match suspension that he picked up against bitter rivals Boca Juniors last week - was on target for the visitors at Estadio Marcelo Alberto Bielsa.
Mori, who served the ban in Thursday's Copa Argentina defeat against Rosario Central - headed home Leonardo Pisculichi's corner in the 67th minute.
River - the only remaining undefeated team in the competition - have collected 25 points from 11 games and are four clear of Lanus.
Ten-man Lanus surrendered a two-goal lead and then came from behind as they salvaged a dramatic 3-3 draw at home to lowly Godoy Cruz on Friday.
Goals on either side of the break courtesy of Victor Ayala and Santiago Silva had hosts Lanus in a commanding position three minutes into the second half.
But Godoy Cruz - third from bottom - levelled proceedings via Ruben Ramirez and substitute Javier Ayovi.
Lanus' woes were compounded when defender Diego Braghieri saw red for a second bookable offence in the 69th minute.
Godoy Cruz made the most of their numerical advantage five minutes later thanks to Claudio Aquino but Lanus refused to give up and earned a share of the spoils as Silvio Romero found the net with 12 minutes remaining.
In other results, Sebastian Penco netted a 90th-minute equaliser as third-placed Independiente drew 1-1 against Defensa y Justicia.
Racing Club bounced back from last week's loss to Atletico Rafaela, routing Estudiantes 4-0.
Velez Sarsfield were also big winners after they emphatically disposed of basement side Olimpo 4-1.
Rafaela threw away a two-goal lead as they drew 2-2 with 10-man Banfield.
Mariano Echeverria and Leandro Marin both scored in the space of three minutes as Boca rallied to beat 10-man Rosario 2-1.
Elsewhere, Carlos Luna's 54th-minute penalty gave Tigre a 1-0 victory over Gimnasia La Plata.
Strugglers Belgrano and Quilmes drew 1-1, while Arsenal and San Lorenzo played out a goalless draw.
