Regular season excellence earned Club Leon , Club Tijuana and Toluca a place in the 2013 Copa Libertadores draw, but it provides no guarantee that their seasons will extend beyond this weekend.

The three top seeds in the Liguilla will proceed through the same wringer as the other five remaining sides with no guarantee of a positive outcome. They face a compressed schedule - sound familiar, MLS fans? - that will see the two-legged quarterfinal ties start on Wednesday and finish by Sunday.

Even with the inherent advantages offered by the reseeding process (the top remaining seed plays the lowest remaining seed in the semifinals) and the tiebreakers (the higher seed advances if the two teams are not separated on aggregate or by the number of away goals scored) as the tournament progresses, it is an arduous process fraught with peril for the top sides.

Previous results display the potential danger ahead. Santos Laguna won the 2012 Clausura as the top seed by defeating second-seeded Monterrey, but that one-versus-two battle marked a rare divergence from the chaos that usually ravages the bracket. The top seed has fallen at the first hurdle in four of the past five Liguillas, a fact that will make Toluca somewhat wary after it edged out Club Tijuana for top spot on goal difference and sealed a date with CD Guadalajara .

Even if Toluca manages to sidestep the recent stumbles afflicting top seeds, the tight fixture list increases the likelihood that one of the other challengers will emerge from the pack to secure the title. The champion may not accurately reflect the evidence offered by the 17-game Apertura, but it will provide plenty of excitement as the field dwindles until the winner is crowned.

FOX Soccer previews the drama set to unfold with a look at each of the matchups slated to take place this week:

#1 Toluca vs. #8 CD Guadalajara (first leg in Guadalajara on Thursday, second leg in Toluca on Sunday)

Three extra goals over the course of 17 games - perhaps including a couple converted by Panamanian striker Luis Tejada (six goals) - handed Toluca the top seed and a more manageable quarterfinal tie against Chivas. It isn't a walkover, however. A recent uptick in form surprisingly pushed Chivas into the postseason, but it hasn't won over the justifiably skeptical Red-and-White supporters. If Toluca can limit the influence of Marco Fabián and Rafael Márquez Lugo (six goals), then it should buck the trend of top seeds making a premature Liguilla exit.

#2 Club Tijuana vs. #7 Monterrey (first leg in Monterrey on Thursday, second leg in Tijuana on Sunday)

This season has already yielded Tijuana a first berth in the Copa Libertadores. Now the Xolos - including United States internationals Joe Corona and Edgar Castillo and budding American defender Greg Garza - will try to secure a first title against a side steeped in Liguilla success. Monterrey relies on a potent front two of Aldo de Nigris and Humberto Suazo to provide the final touch and supplements their predatory instincts with a deep, experienced and talented supporting cast. Tijuana must rely on its collective strength (one defeat suffered in 17 league matches, fewest in Liga MX) to progress to the semifinals.

#3 Club Leon vs. #6 Cruz Azul (first leg in Mexico City on Wednesday, second leg in Leon on Saturday)

Leon made a significant impact in its first top-flight season in ten years, but it faces a difficult task to keep the momentum rolling against Cruz Azul. Christian Gimenez and Mariano Pavone (seven goals) lead a talented, but underachieving, group that also includes emerging winger Javier Aquino, Mexico number one Jesús Corona and veteran midfielder Gerardo Torrado. Leon doesn't possess that sort of star power, but the presence of Uruguayan striker Nelson Maz (eight goals) and recent Mexico call-up Carlos Peña (six goals) guarantees the recently promoted side won't succumb without a fight.

#4 Club America - #5 Monarcas Morelia (first leg in Morelia on Wednesday, second leg in Mexico City on Sunday)

Do not let the decent seed obscure the reality of the situation: America supporters aren't entirely happy with their club ahead of the Liguilla. One of the two largest sides in the country finished behind three relative minnows despite boasting the league's top scorer (Ecuador international striker Christian Benítez) and the league's best defense (tied on 15 goals conceded with Cruz Azul and Tijuana). This series against Morelia provides a chance to partially atone for the 3-1 home defeat to Chivas last month and the persistent record of underachievement over the past few years.