Boca's first win in four matches allowed arch-rivals River Plate to take the outright lead in the Argentine Apertura championship despite being held 0-0 by title holders Argentinos Juniors at their Diego Armando Maradona ground.
River have 10 points from four matches, one point more than Velez and Arsenal, with San Lorenzo, last season's Apertura winners Banfield and Godoy Cruz on eight.
Borghi discovered what the pressure could be after bad results at Argentina's most popular club following Boca's shock 2-0 defeat by promoted All Boys last weekend and said Sunday's match with Velez would be decisive.
There was renewed fight in Boca after some tepid play in two successive defeats and Viatri took his championship tally to three when he headed Boca's second midway through the second half.
Independiente, another of Argentina's traditional Big Five, thought they had ended a poor start to the championship with a 1-0 win in midweek over Argentinos in the Copa Sudamericana, the Europa League equivalent in South America.
Instead, Daniel Garnero's team are bottom with one point after they were ambushed 2-1 at home by modest Arsenal, prompting fans to demand the return of last season's coach Americo Gallego who did not have his contract renewed.
