Racing Club squandered a chance to share the Argentine Clausura lead after losing 2-1 to Tigre on Saturday.
Racing, which finished with only nine men, remains on 12 points, three behind Estudiantes.
Mariano Pernia headed in the opening goal for Tigre in the 23rd minute, and Denis Stracqualursi extended the lead when he leaped high in the 51st to score from an 8-meter header off a free kick.
Claudio Yacob cut the lead to 2-1 when he headed in a free kick in the 77th minute.
Racing's Lucas Licht was sent off in the 43rd minute and Luis Farina was ordered from the field in the 85th.
Velez Sarsfield, the runners-up last season, moved a point behind the leaders with a 2-1 victory at Olimpo.
Ricardo Alvarez scored in the first minute for Velez before Martin Rolle equalized in the 39th. Emiliano Papa scored the winner in the 51st. Velez has 14 points, while Olimpo stayed on 13.
Struggling clubs Newell's and Arsenal played out a 2-2 draw.
Arsenal took a 2-0 lead on first-half goals by Luciano Leguizamon and Mauro Obolo, but Newell's equalized in the second to delight the home crowd. Juan Cobelli scored in the 46th and Sergio Almiron leveled in the 53rd.
All Boys and Lanus played a scoreless draw.