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 tomorrow [Tuesday] 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 (seven) and Martin Zapata (23pen) set up the win despite Rodrigo Erramuspe (35) 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.