They've both won the Copa America more times than anyone else. Fourteen times apiece to be exact.
Argentina, the home team, bears the weight of an expectant nation, frustrated by 18 years without a major tournament victory.
Uruguay, coming off a surprising semifinal run in last year's World Cup, didn't exactly sparkle in first-round play.
They come head to head tomorrow in the quarterfinals. Tune in at 6:15 p.m. ET for this year's Battle of the Rio Plate.
Supporters of Argentina cheer on their team before a first-round match. (Omar Torres/AFP/Getty Images)
A Uruguay fan cheers for her team before the start of a first-round match. (Alejandro Pagni/AFP/Getty Images)
Argentine forward Gonzalo Higuain vies for the ball against Costa Rican defender Oscar Duarte. (Antonio Scorza/AFP/Getty Images)
Uruguayan defender Diego Lugano runs for the ball during a first-round match against Mexico. (Daniel Garcia/AFP/Getty Images)
The starting line-up for the Argentine national soccer team. (Cris Bouroncle/AFP/Getty Images)
Uruguay's starting line-up poses with Suri, the Copa America mascot. (Daniel Garcia/AFP/Getty Images)
Argentine goalkeeper Sergio Romero punches the ball during a match against Colombia. (Antonio Scorza/AFP/Getty Images)
Uruguayan forward Diego Forlan heads the ball to the goal during a match against Chile. (Alejandro Pagni/AFP/Getty Images)
Argentina's star player, forward Lionel Messi, prepares for a corner kick during a first-round match. (Daniel Garcia/AFP/Getty Images)
Uruguay's star player, forward Diego Forlan, eyes the ball during a first-round match. (Rodrigo Arangua/AFP/Getty Images)
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Hannah McGoldrick contributed to this story.