Martin Palermo and Lucas scored either side of half time to give Boca Juniors a 2-0 win over Huracan in the Argentine league on Sunday.
Boca's rival River Plate drew 2-2 at Godoy Cruz meaning only a point separates the two teams, with River in eighth on 17 points and Boca a point further behind in 10th.
Also Saturday, Racing Club beat defending champion Argentinos Juniors 2-1 and Olimpo had a 1-0 win over Lanus.
Estudiantes leads the standings with 26 points from 11 matches, three ahead of Velez Sarsfield and Arsenal.
Boca striker Palermo controlled the ball on the edge of the area and swiveled to send a left-footed volley into the far side of the net to open the scoring against Huracan in the 44th.
Replays showed Palermo had controlled the ball with the help of his hand, but the referee Luis Alvarez judged the contact to be accidental.
Boca's second came in the 67th minute when Cristian Chavez dribbled into the box on the left, committing three defenders into the tackle. The ball broke for Viatri, who fired a low shot past goalkeeper Gaston Monzon from 10 yards (meters).
Palermo now has six goals in the Apertura tournament, one behind Velez strikers Santiago Silva and Juan Manuel Martinez.
River Plate also looked set for victory when Francisco Pavone beat the Godoy Cruz defense and scored for a 2-1 lead in the 64th minute.
However, Godoy Cruz substitute Cesar Carranza pulled the home side level with a 79th-minute strike to keep his side above River in seventh position on goal difference.
Leonardo Sigali conceded an own goal to give River the lead in the 41st minute, while David Ramirez got Godoy's first equalizer in the 53rd.
Elsewhere, Hernan Grana scored in the 48th minute to give third-bottom Olimpo a 1-0 home win over sixth-placed Lanus, and Giovanni Moreno hit two second-half goals as Racing Club beat Argentinos Juniors.
Racing is ninth in the standings, with Argentinos in 15th.
