Chile took neighbourly bragging rights at the Copa America, winning their Pacifico clasico with Peru to top Group C while Uruguay edged Mexico to book a quarter-final with hosts Argentina.
Four-time finalists Chile have been playing some of the best football at the championship and on Tuesday deservedly saw off two-time champions Peru - though it took an injury-time own goal from Peruvian defender Andre Carrillo to settle the encounter at Mendoza.
Both sides went into the game with the pressure largely off as they had garnered four points from their opening two games to guarantee further progress.
A flare-up between Jean Beausejour of Chile and Peru's Giancarlo Carmona proved a lowpoint, both men sent off on the hour by Brazilian referee Salvio Fagundes - to the fury of Peru coach Sergio Markarian, who contested the wisdom of Fagundes.
"This is the same one who deprived Colombia of a legitimate win against Argentina," insisted Markarian, referring to a penalty appeal denied the Colombians when their forward Radamel Falcao Garcia felt he had a claim for a foul in the box.
Markarian was scathing about the red cards.
"Carmona did not deserve to be sent off - though Beausejour did. And that changed the game," he blasted.
Beausejour apologised to his teammates afterwards.
"I am sorry. There is no justification for what I did," said Beausejour after starting the set-to which saw him and Carmona head for an early bath.
Carmona was also contrite.
"I feel responsible for the defeat," he groaned.
Uruguay meanwhile snapped out of their insipid early tournament form with Alvaro Pereira netting on the quarter-hour against the Mexicans at La Plata following an error by Mexico keeper Luis Michel.
Veteran Uruguayan striker Diego Forlan ran the show, having a hand in the goal while winning a record-equalling 79th cap for his country to go level with former keeper Rodolfo Rodriguez.
Another two goals and Forlan, whose last strike in sky blue came in the World Cup third-place play-off loss to Germany a year ago, will also share the national scoring record with Hector Scarone, who netted 31 times between 1920 and 1930.
Saturday's quarter-final against the renascent, Lionel Messi-inspired Argentinians, will be eagerly anticipated as both the hosts and the Uruguayans have won a joint record 14 continental titles.
The celeste also are the only team in 95 years of the tournament to deny Argentina victory on the home front - Argentina have won six out of eight events they have hosted but came a cropper to their near neighbours on the other two occasions, back in 1916 and 1987.
Uruguay coach Oscar Tabarez says he is looking forward to the encounter.
"But it will be a very tough hurdle for us. It will be do or die and now the tournament is really beginning in earnest.
The duel will take place at the Santa Fe stadium nicknamed the elephants' graveyard, scene of numerous domestic shocks in Argentine football.
The Mexicans meanwhile go home with zero points after electing to come here with essentially an under-22 team, the seniors having a rest after winning the CONCACAF Gold Cup last month.