The match ended Boca's unbeaten record in the Argentine championship and knocked them off the top of the table.
Fernando Cavenaghi headed the winner as River went top of the Clausura championship with 32 points from 14 games, one point ahead of Boca, despite losing injury-plagued Chilean striker Marcelo Salas early in the game.
From Reuters:
'Boca finished with nine men after midfielder Jose Calvo and striker Carlos Tevez were sent off in the second half. To add insult to injury, the defeat came before a 56,000 crowd in their usually impregnable Bombonera stadium. River had defender Eduardo Tuzzio dismissed.
Calvo was sent off three minutes into the second half for kicking Luis Gonzalez and Tevez followed with eight minutes left for a wild challenge on Horacio Ameli as his frustration got the better of him.
Tuzzio followed two minutes later for another bad tackle. With five rounds of matches to play, the championship now appears to be a two-horse race between the old rivals.'