Breaking down the red-hot Sudamericana matchups

	Antonio 'Zinha' Naelson's Toluca is one of two Mexican clubs trying to replicate Pumas' final showing in last year's Sudamericana. AP
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It looks as if, once again, Mexican clubs have a long way to go before they can truly compete with top South American opposition.

That much looked true Tuesday night, as Pachuca and Toluca made their less-than-impressive Copa Sudamericana debuts. Both sides struggled against what were deemed "assessable opponents."

Pachuca was fortunate to escape with a 2-1 loss against Tolima. If it wasn't for some outstanding interventions from goalkeeper Miguel Calero, the Colombians could easily have put the series out of their reach.

Toluca, widely regarded as Mexico's top side, edged Ecuador's El Nacional 1-0. The Diablos Rojos may have gotten the win, but it was a poor display. Besides Zinha, their players were incapable of unsettling vulnerable opposition.

Early signs indicate that if either of these two Mexican clubs succeed in progressing to the quarterfinals, they are likely to be outshined by superior teams.

Here's a breakdown of the rest of the round-of-16 matchups. The pick of the bunch is definitely the clash between traditional heavyweights Nacional and Boca Juniors.

River Plate vs. Atlético Paranaense

River fans haven't had too much to cheer about in the last few years, a stark contrast to the fans of archrival Boca Juniors. A major continental title is just what the Millonarios need, especially as their last crown was the 1996 Copa Libertadores, when they were captained by the great Enzo Francescoli. River has picked up in recent weeks after a slow start to its domestic campaign, but it's still far from its best.

This is where Atlético Paranaense may have the upper hand; the Brazilians cruised into the last 16 after a 4-1 aggregate demolition of city rivals Paraná. The Furacão pays heavy emphasis to the attack but will have to rely on a firm defense in order to overcome the Argentines, who are also particularly dangerous at front. Expect an open contest between two potential title candidates.

The pick: River.

San Lorenzo vs. Santos FC

This promises to be an intriguing matchup, as it brings together two teams that play entertaining attacking soccer. San Lorenzo, which won the inaugural Copa Sudamericana in 2002, has done well to overcome last month's 7-1 mauling against Boca, with some confidence-boosting results. The Ciclón can be unpredictable at times but will be motivated by the fact that a victory against Santos could help put its inconsistency behind it. Although leading scorer Andrés Silvera is out injured, San Lorenzo can count on Peruvian striker Roberto Jiménez, who is equally as lethal.

Santos counters with numerous skillful players, including attacking midfielder Rodrigo Tabata, amongst the scorers in the Peixe's 3-0 win over Flamengo last Sunday. The Brazilians are one of the most dangerous sides in the competition -- much of its strength is outlined by the individual quality of its players. Vanderlei Luxemburgo is well aware that his team is more than capable of defeating the Argentines and is likely to stick to his normal game plan in order to pick up a positive result on the road before deciding the series at the Vila Belmiro.

The pick: Santos.