Grêmio (7) vs. São Paulo (10)

	Prolific scorer Humberto Suazo leads Colo-Colo against Club América in what should be one of the best matchups of the round of 16. AP

It's survival of the fittest. The Libertadores has been characterized by flamboyant all-Brazilian affairs over the years, including the finals of the last two editions. And this matchup is no exception. Both sides have demonstrated that they have enough talent to proceed to the final stages, and although most would back three-time winner São Paulo, the southerners are no slouches when it comes to these types of matches. An extra ingredient to spice up the matchup is that former São Paulo hero Amoroso will be defending the colors of Grêmio.

Rating: Five stars
The pick: São Paulo

Vélez Sársfield (6) vs. Boca Juniors (11)

If someone had asked Boca manager Miguel Ángel Russo which club he would have liked to avoid in the last 16, he would have surely picked the team he used to coach. It's no secret that over the last few years, Vélez has consolidated itself as the second most-powerful club in Argentina. But the Fortín face a daunting task against a well-reinforced Boca side. Los Xeneizes may be highly inconsistent, but are fresh off an emphatic 7-0 demolition of Bolívar last week. Juan Román Riquelme's team is still the most complete in the competition, but will have to be at its best in order to overcome Vélez. Adding to the drama? The man who took Ángel's place at Vélez is Ricardo Lavolpe, the scapegoat in Boca's late-season collapse last year.

Rating: Five stars
The pick: Boca

Libertad (3) vs. Paraná (14)

This match brings together two sides with highly contrasting styles of play. On one side we have Libertad, the ruthless Paraguayans who like to play on the counterattack; on the other, a highly entertaining Paraná side. From both teams' displays so far in the competition, it's difficult to know what to expect from the series. Libertad has more experience at this level, but you can be sure that the Brazilians will give it all they've got.

Rating: Three stars
The pick: Paraná

Necaxa (5) vs. Nacional (12)

Nacional has reestablished itself as a leading club with some impressive campaigns over the last couple of years. This season, it has continued its gradual improvement after eliminating defending Libertadores (and Club World Cup) champion Internacional from the Group of Death. But Nacional will come into its clash with Necaxa on a low after a devastating 3-0 defeat at the hands of bitter rivals Peñarol in the Uruguayan Clásico last Sunday. Unless it recovers from that heavy defeat, Nacional will struggle against a solid Mexican side that will be boosted by the return to form of prolific Brazilian striker Kléber Boas.

Rating: Four stars
The pick: Nacional

Toluca (4) vs. Cúcuta Deportivo (13)

This is probably the least attractive matchup of the round of 16, pitting two clubs with no Libertadores history. Regardless, it still promises to be an intriguing contest, as both clubs have a lot to prove. Cúcuta clinched its spot with a stunning 4-3 victory over fellow Colombian club Deportes Tolima, while Toluca edged Boca for first place in its group. Expect an even contest, but if form means anything, Toluca will advance.

Rating: Two stars
The pick: Toluca