Cerro Porteño welcomed Boca Juniors to the redeveloped Estadio General Pablo Rojas for its reinauguration on Saturday evening and while the completion of work was reason to celebrate for the locals, an injury time winner handed victory to Boca.
Without Fernando Gago in midfield, Boca were not as impressive as they have been in previous friendlies and without that control, the Argentine champions were second best during the opening 45 minutes.
Boca improved after the break and eventually Wilmar Barrios poked the visitors ahead from close range.
That 76th minute goal looked to be enough but as the game edged into injury time, Diego Churín hooked in an equaliser on the turn.
However, there was still time for Frank Fabra to burst into the Cerro Porteño penalty area and cut the ball back for youngster Gonzalo Maroni to tap in the winner.