The draw left title holders Boca one point ahead of Arsenal, who beat Argentinos Juniors 3-1 on Friday, in a tight title race in the Clausura championship and whom they meet at their Bombonera home next weekend.
Tigre can also climb within a point of Boca if they win Sunday's home game with San Lorenzo, while Newell's Old Boys are just two behind after Saturday's 2-1 home win over Independiente in Rosario.
Banfield had Rodrigo Pepe sent off after only four minutes for a foul on fellow midfielder Pablo Ledesma.
Defender Agustin Alayes then headed struggling Banfield, champions in the 2009 Apertura under present Boca coach Julio Cesar Falcioni, into the lead early in the second half.
Boca equalised four minutes later with an own goal by Santiago Ladino but failed to take all three points despite boasting three of the championship's best forwards in Walter Erviti, Dario Cvitanich and Santiago Silva, who were all in Banfield's 2009 team.
"We still have our fate in our hands. If we'd been told that with two matches to go we would have a one-point lead we'd have taken that," Boca captain Juan Roman Riquelme told reporters.
