Boca vs. River headlines Copa Libertadores semis

Ramon Diaz: Superclasico always full of emotion (1:17)

River Plate manager Ramon Diaz spoke ahead of his side's 'Superclasico' with Boca Juniors and discussed the history behind the fixture (1:17)

In the early hours of Thursday a violent storm broke over Buenos Aires -- mere prelude, perhaps, to the matchup in the semifinal of the Copa Libertadores that has been both desired and dreaded.

Historic rivals Boca Juniors and River Plate will meet over two legs in October for the right to play in this year's final. Last year, of course, it all proved too much and, following fan violence outside River's stadium, the decisive second leg was controversially switched to Madrid. The rumblings have yet to die down, with the case under review by the Court of Arbitration for Sport.

There was no chance of a home and away meeting in the final this year -- the format has been changed to a one-off game on neutral ground -- but as fate would have it, the teams will clash instead in the semis.

Boca's place in the last four was never in doubt after their hugely impressive first leg win, dealing immaculately with the altitude of Ecuador's Quito to beat Liga, often referred to as LDU, 3-0. At home they merely administered their advantage as the goalless draw was chiefly notable for an appearance near the end by the veteran Italian midfielder Daniele De Rossi.

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River had to work harder, and ended up sweating in the early evening heat of Asuncion, the capital of Paraguay. They flowed in fine style during last week's 2-0 win at home to Cerro Porteno, but the away leg always looked tricky.

In Buenos Aires, Cerro Porteno had shown their threat in the air. The Paraguayans had a 100% home record in the competition and were backed by a huge crowd, who arrived full of hope. Local rivals Olimpia have lifted the trophy three times; Cerro Porteno have never got beyond the semis and fans hoped that their 40th campaign might be the lucky one.

They could hardly have started better. River were ragged, giving the ball away cheaply, and the Paraguayans broke down the right. Joaquin Larrivey curled in a splendid cross, and veteran Nelson Haedo Valdez got in front of his marker to glide a wonderful header inside the far post.

There were chances for the Paraguayans to draw level on aggregate, but River coach Marcelo Gallardo ordered his team to be more compact in order to pick up the second ball. And, soon after the restart, Matias Suarez was played behind the defensive line; his shot was blocked by the keeper, and the ball ran loose. Nico De la Cruz was first to it, with plenty of Paraguayan defenders around him. Had he taken a touch to bring the ball under control then the chance would have gone -- instead he fired home a magnificent first time shot that flew in off the bar.

It was a goal worthy of deciding any tie, and was especially sweet for the scorer. De La Cruz was arrested earlier in the week by Paraguayan police for an incident that allegedly took place three years ago during an Under-20 game, before he was released on bail. His goal got River a 1-1 draw, out of a tight spot and into the semifinals.

So, with River and Boca set to renew hostilities, the path was open for two more teams. Gremio will be one as they came through the all-Brazilian tie with Palmeiras.

Gremio had lost the home leg 1-0, and were soon a goal down against a side which boasts an excellent defensive record. But teams can often be vulnerable soon after they have scored; Palmeiras lost concentration and Everton, the little hero of Brazil's Copa America triumph, scored with a cute cross volley. Inspired, he then dribbled right through the heart of the rival defence. The keeper came out to block and the ball fell for Alisson to seal a 2-1 win.

With that, three of the 2018 semi finalists had sealed their place in 2019's version. The newcomer is Flamengo, the Rio de Janeiro giants who have been punching below their weight for years in this competition. Hiring Portuguese coach Jorge Jesus in the middle of the year galvanised the team, who are playing a swashbuckling brand of football that made them worthy winners over fellow Brazilians Internacional.

Flamengo were 2-0 up from the first leg. At home in Porto Alegre, Inter bizarrely went with the same line up, with no pace to examine Flamengo's high defensive line. They were lucky not to concede in the first half, but made attacking changes and started to turn the screw after the interval.

Rodrigo Lindoso headed home from a free kick, but the five minute delay before VAR validated the goal did Inter few favours. They lost momentum and panicked, before being naively caught on the break when they still had over 10 minutes to draw level on aggregate. Bruno Henrique charged forward and set up Gabriel 'Gabi-goal' Barbosa to slide home and make certain what promises to be an attractive semifinal against Gremio.