River Plate's Argentine title ambitions took a hit Sunday with a 2-0 loss to last-placed Argentinos Juniors.
River is now third in the standings, three points behind league leaders Newell's Old Boys which can go six points clear with a win over All Boys on Monday with just three rounds remaining in the Argentine first division.
In other matches Sunday, second-placed Lanus could only draw 0-0 against Belgrano, leaving it three points off the lead, while struggling Boca Juniors drew 1-1 with Velez Sarsfield in La Bombonera.
Julio Barraza opened the scoring for Argentinos in the 81st minute, converting from a corner with a low, first-time volley that went between goalkeeper Marcelo Barovero's legs.
Rodrigo Gomez took the game beyond River in the 87th when he finished into the roof of the net after Pedro Hernandez had rounded goalkeeper and squared the ball to leave a simple chance.
River thought it had taken the lead in the 32nd, but a Manuel Lanzini goal was ruled offside, amid protests from the River players. TV replays showed the goal should've stood.
Boca remains second to bottom of the league after its draw with Velez.
Federico Insua curled in a perfect left-footed free-kick from the edge of the penalty area to hand Velez the lead in the 14th minute, with Nicolas Blandi heading in for the equalizer in the 35th.
In Sunday's other game, Union defeated Colon 1-0, with Damian Lizio scoring the goal from the penalty spot in the 53rd.
In matches Saturday, Independiente and Estudiantes drew 0-0, as did Rafaela and fourth-placed San Lorenzo. Godoy Cruz won 3-0 against Arsenal to move into fifth place.
On Friday, Quilmes defeated Racing 1-0 thanks to a 9th minute goal from Martin Cauteruccio.
As well as Newell's vs. All Boys, Tigre plays San Martin on Monday.
