Boca Juniors suffered an unexpected 3-2 loss to Velez Sarsfield at the Bombonera stadium on Sunday, and dropped down to third place with only four matches remaining this season.
Mariano Uglessich headed Velez into the lead in the 17th minute when he was left unmarked inside of the Boca area. Six minutes after the break Nicolas Cabrera doubled Velez's advantage with a brilliant individual effort that stunned the strong 45,000 crowd at the Bombonera.
In the 58th minute Juan Roman Riquelme struck the underside of the crossbar with a finely executed free kick, and Juan Forlin scored from the rebound. But five minutes later Velez's advantage was restored by Jonathan Cristaldo after a brilliant finish.
Rodrigo Palacio, who returned to action after a lengthy spell out came on from the bench, and pulled a goal back for Boca six minutes before full time.
San Lorenzo was held to a thrilling 3-3 draw by Newell's Old Boys in a fiery encounter that saw three men sent off. Despite taking a two-goal lead through Pablo Barrientos San Lorenzo couldn't hold on and Newell's forced the draw.
Adrian Gonzalez restored San Lorenzo's advantage from the penalty spot (65'), but goals from Leonel Vangioni (80') and German Re (84') gave Newell's a precious point. San Lorenzo remains in the top spot with 30 points from 15 matches.
Tigre shares the top spot with San Lorenzo after a comfortable 2-0 victory over Godoy Cruz. Martin Morel scored both of Tigre's goals (12' & 45'). Diego Cagna's side is on track for the first title of its 106-year history, after a memorable campaign so far.
Argentine Clausura champions River Plate escaped from bottom place after a tight 1-0 victory over city rivals Independiente in the official debut of interim coach Gabriel Rodriguez.
Colombian striker Radamel Falcao Garcia grabbed River's winner in the 65th minute with a well-directed header. It was River's first victory after 13 games this season.
In the match that inaugurated the round on Friday night, Banfield came from behind to draw 1-1 with Lanus in a tight Southern Buenos Aires derby. While Gimnasia y Esgrima de La Plata defeated San Martin de Tucuman 1-0 with a late strike from Mariano Messera.
In the other matches, Rosario Central picked up a vital 2-0 victory over Huracan in La Paternal, Arsenal de Sarandi beat Gimnasia de Jujuy 1-0, and Colon de Santa Fe defeated Racing Club 2-0 in Avellaneda.
Finally, Argentinos Juniors thumped Estudiantes de La Plata 5-0, only three days after both teams tied 1-1 in the semifinals of the Copa Sudamericana.