Arsenal Sarandi could only draw 1-1 at Estudiantes, leaving them three points off the top of the Clausura table with three rounds remaining.
Emilio Zelaya put Arsenal ahead from the spot after 17 minutes, but Duvan Zapata levelled two minutes before the break.
The draw left Arsenal three points behind Boca Juniors, who beat Godoy Cruz on Sunday, and level with Tigre.
Two second-half strikes gave Velez Sarsfield a 2-0 win at Colon Santa Fe. Manuel Martinez opened the scoring six minutes after the break and Augusto Fernandez made the points safe a minute from time.