BUENOS AIRES, Dec 3 (Reuters) - Boca Juniors, needing to beat Belgrano to win the Argentine championship with a game to spare, lost 1-0 as second-placed Estudiantes drew 2-2 at Argentinos Juniors to keep the title race alive on Sunday.
Boca are three points clear of Estudiantes with one match to play, providing a dramatic twist to a championship which had previously been more notable for crowd violence and intimidation.
Boca fans in the 42,000 crowd in Cordoba had been celebrating the title after Estudiantes went behind.
The celebrations subsided dramatically as Belgrano went ahead and Estudiantes, who had won their last 10 games, went 2-1 in front to effectively move within one point of Boca.
Argentinos's stoppage-time equaliser left Boca three points ahead and needing only to draw next Sunday's game at home to Lanus to clinch their third successive title.
If they lose and Estudiantes beat Arsenal, the competition will be settled by a playoff match.
Boca enjoyed the better of the early exchanges against Belgrano but appeared to relax after hearing that Argentinos had taken a first-half lead against Estudiantes.
They paid the price on the hour when Franco Peppino scored with a clinical finish to hand them only their second defeat in 18 outings.
In the other game, striker Jorge Quinteros headed home a cross from Leonel Nunez to put Argentinos Juniors ahead after 25 minutes.
Estudiantes, showing the same fighting spirit which characterised their coach Diego Simeone during his playing days, hit back through Pavone in the 78th minute before Juan Sebastian Veron put them ahead with three minutes left.
Argentinos, however, had the last laugh as Choy Gonzalez equalised in the second minute of stoppage-time.
In other matches, third-placed River Plate crashed to a shock 2-1 home defeat by lowly Nueva Chicago.
Ernesto Farias gave Daniel Passarella's team a second-minute lead but the visitors hit back with second-half goals from Federico Higuain, the older brother of River striker Gonzalo, and Jorge Martinez.
Beleaguered San Lorenzo coach Oscar Ruggeri was jeered by his own fans before and during his team's 2-2 draw at Arsenal.
Pablo Quatrocchi gave San Lorenzo a fourth-minute lead, Lucas Valdemarin scored twice to put Arsenal ahead and Andres Silvera equalised three minutes before the break.
San Lorenzo, who started as potential title challengers, are eighth.