BUENOS AIRES, April 20 (Reuters) - River Plate slumped to their first defeat of this year's Clausura championship when they were beaten 2-1 by midtable Rosario Central on Sunday.
Estudiantes took advantage of River's slip to pull level on points at the top of the standings by drawing 1-1 away at Tigre.
River started well when Diego Buonanotte gave them a 20th minute lead, scoring with a shot which went in off the post.
But Central turned the game around before halftime when Emilio Zelaya scored from outside the penalty area and Colombian Martin Arzuaga fired the winner with a shot on the turn.
Jose Basanta scored early in the second half for Estudiantes to earn them a point at Tigre, who had taken the lead through Martin Galmarini after half an hour.
River and Estudiantes, coached by former Argentina team mates Diego Simeone and Roberto Sensini respectively, have 24 points from 11 games.
On Thursday, Estudiantes were officially awarded the points from last month's match away to Racing Club, which was abandoned in the second half by a crowd riot.
Estudiantes were 2-1 ahead at the time.
Boca Juniors are one point behind the leading pair after beating Newell's Old Boys 2-1 with an 80th minute goal from striker Martin Palermo.
Midfielder Juan Roman Riquelme made his return for Boca, the only team still unbeaten, after a one-month injury layoff.
Fourth-placed San Lorenzo's run of six successive wins ended when they lost 2-1 at Argentinos Juniors, Gabriel Perez scoring the winner in the last minute.