Boca Juniors' place at the top of the Argentinian Clausura is under threat after they could only drew 1-1 at Belgrano Cordoba.
Boca needed a Walter Erviti leveller on 49 minutes to take a point, after Matias Gimenez opened the scoring on 23 minutes, to present Newell's Old Boys with the chance to take over that the top.
Newell's take on Arsenal on Monday knowing victory will move them two points clear at the summit.
All Boys moved up to fifth, two points adrift of Boca, with a 2-1 home win over Union Santa Fe. Early goals from Emanuel Perea and Martin Zapata set up the win despite Rodrigo Erramuspe pulling a goal back.
Nicolas Tagliafico's last-minute equaliser earned Banfield a 1-1 draw with San Lorenzo, who had led when Carlos Bueno struck on 64 minutes.
Godoy Cruz were held to a goalless draw by 10-man Independiente, who had Adrian Argacha dismissed six minutes from the end.