Boca Juniors overcame arch-rivals River Plate on Sunday on penalties, despite the heroics of River's fifth-choice goalkeeper who made his debut and put on an inspired display after 15 of the team's players tested positive for the COVID-19 virus.
Leo Diaz, 21, had never appeared for the club's reserves, never mind their first team but was superb during a game that ended 1-1 after 90 minutes.
"The keeper made three or four great saves," said Boca captain Carlos Izquierdoz.
Diaz had no chance when Carlos Tevez scored a fine diving header to put Boca 1-0 up after 11 minutes.
But the youngster then saved from a string of Boca players, including Tevez on at least two occasions.
Julian Alvarez equalized for the visitors midway through the second half to take the game to penalties, with Diaz saving one of Boca's five spot kicks.
However, his teammates missed two of their four, condemning River to a 4-2 defeat.
It was the first time Boca have beaten River in a knockout match since 2004 and takes them into the semifinals of the Copa de la Liga, this year's national championship in Argentina.
Diaz was the only keeper available after four others tested positive on Saturday and celebrated his selection by getting a new haircut, incredibly, without a mask.
"I congratulated him," Tevez said about the keeper. "He was in his house and they called him to play. You have to take your hat off to him."