Leaders face testing time
© AFP

In a week when the group stage of the UEFA Champions League kicked off amid much fanfare, top teams the length and breadth of planet football will be looking to make a few headlines of their own this weekend in their domestic championships. In Argentina, Brazil, Mexico and the USA, for example, a host of enticing fixtures could add further twists to their league title races. As ever, FIFA.com is on hand to preview the pick of the action.

Argentinian Apertura: San Lorenzo out for more
After an early exit from the Copa Sudamericana, San Lorenzo have vowed to redouble their efforts to reclaim the Argentinian championship they last won in June 2007. Heading into matchday 7, all the signs are that Miguel Angel Russo's side are serious about their promise. With the arrival of Santiago Solari, they are already leading the way in the Apertura and growing in confidence. Next up for San Lorenzo is a home fixture against Colon de Santa Fe, who currently trail them by three points and have not won in Almagro since 2005.

Big game: Aside from the aforementioned clash at the Nuevo Gasometro, another standout fixture this weekend will be the meeting of Boca Juniors and Tigre at the Bombonera. With the teams joint-second on 11 points, whoever wins could gain a vital edge in the title race before the second half of the Apertura.

Player to watch: Lionel Nunez, who arrived at Independiente via Olympiacos of Greece, has already begun paying his way in goals. After a hat-trick in his side's last outing against Gimnasia de Jujuy, the striker will be hoping for more this weekend and help secure his side's first away win this season.  Standing in his way, however, will be Fernando Gamboa's battling Newell's Old Boys outfit, who have ambitions of their own.

Brasileirao: Gremio to bounce back?
After a surprising reverse to Goias on their last outing, Gremio will be hoping to get back to winning ways when they travel to Atletico PR this Sunday on matchday 26 of the national championship. The Porto Alegre club, who recently celebrated their 105th anniversary, will be aiming to take advantage of their opponents' irregular form and lowly 16th place to stay ahead of the chasing pack at the top.

Big game: Palmeiras and Vasco Da Gama will be in very different moods when they meet this Sunday after their Copa Sudamericana showdown in midweek. On that occasion the Sao Paulo outfit ran out 3-0 winners to progress to the next round. Will they manage to do it again this weekend and catch Gremio at the summit or will there be a measure of revenge for the Carioca side?

Player to watch: Fans of Palmeiras will be eagerly awaiting the debut of Roque Junior, recently signed from Qatari side Al-Ryyan. The 32-year-old Brazilian defender, a world champion at Korea/Japan 2002, will be returning to the club where he dazzled as a youngster between 1995 and 1999.

Mexican Apertura: Pumas and San Luis take centre stage
All eyes this weekend in Mexico will be on the clash between Pumas and San Luis, respective leaders in Group 2 and 3 of the championship. The showdown, which takes places at Pumas' Estadio Universitario, will give the in-form hosts a good opportunity to register their first home win over Raul Arias's battling outfit. One interesting footnote is that neither coach will be on the bench for the game as both are serving suspensions.

Big game: The clash of the leaders aside, also in the spotlight will be the visit of Group 1 frontrunners Atlante to the Estadio Azteca to face America. Ramon Diaz's charges are desperate for points in what has so far been a testing championship for them, while their visitors from Potosi will be hoping to hold onto top spot and avoid what would only be their second defeat of the season.

Player to watch: Venezuela's Giancarlo Maldonado has found the net against America in the last two meetings of the sides. Will the San Luis man make it three in a row this weekend and heap more misery on the struggling Águilas?

USA Major League Soccer: No time to lose for New England
Columbus Crew's 3-1 win over New York Red Bulls on Thursday night moved the Ohio side six points clear at the top of the Eastern Conference and heaped further pressure on their immediate pursuers New England Revolution. Steve Nicol's side face a testing away-day assignment against Colorado Rapids this Sunday but will not be lacking in confidence after their 4-0 demolition of Chivas USA the previous week.

Big game: Over in the Western Conference, the clash of Real Salt Lake and Chivas USA, second and third respectively, provides a timely opportunity for one of them to close the gap on runaway section leaders Houston Dynamo.

Player to watch: All eyes will be on Brian Ching again this weekend as the Houston striker looks to extend his rich vein of form. In his sights this time will be San Jose Earthquakes as the Texan side look to maintain their comfortable lead in the standings.