Cruzeiro bucked the trend as it left Argentina with a win and a priceless away goal Thursday, while Guarani won at home.
Marquinhos was on target as Cruzeiro became the first away team to score during the quarterfinals of the Copa Libertadores, trumping River Plate 1-0 in Buenos Aires.
No away team in the other three last-eight fixtures had scored on the road, but Cruzeiro put an end to that thanks to midfielder Marquinhos and his 82nd-minute strike at El Monumental in the Argentine capital Thursday.
River - taking part in the quarters after rival Boca Juniors was expelled from the CONMEBOL competition - came unstuck eight minutes from time, having failed to clear its lines.