With the UEFA Champions League group stage over and the midpoint of the season fast approaching, this is the time of year when many future champions make a decisive breakaway at the top of the standings. FIFA.com previews the forthcoming action in Europe's major championships.

Premier League: North-west versus south-east
The two leading London clubs are blazing a trail in the Premier League this term, but their counterparts from Liverpool are lagging badly after disappointing campaigns so far. This weekend presents the teams from the Mersey with a chance to redress the situation, at least in part. Everton, unexpectedly struggling in 15th spot, travel to leaders Chelsea for a rerun of last season’s FA Cup final. Liverpool, still smarting from an ignominious Champions League exit and treading water in seventh, entertain third-placed Arsenal.

Champions Manchester United are second and will obviously be hoping the Blues and the Gunners slip up. However, Sir Alex Ferguson’s injury-hit side face a thorny challenge with the visit of fifth-placed Aston Villa, themselves undefeated since early November.

The question: Can Fernando Torres, just back from a long injury lay-off, help Liverpool get their season back on course at home to Arsenal?
The big game: Liverpool–Arsenal, Sunday, 17.00 CET, Anfield
The quote: "If we get back to our full-strength team, and we get people fit, we’re confident we are good enough to finish in the top four," Steven Gerrard, Liverpool captain

La Liga: One derby and plenty of pressure
The forbidding surroundings of the Mestalla provide the focus in Spain. Real Madrid’s star-studded ensemble visit Valencia on the back of last week’s defeat by Barcelona in El Clásico, knowing they can hardly afford to drop points. However, it is a big ask: Unai Emery’s men are undefeated since late September and lie just a place below Real.

The Catalan leaders, who head to Abu Dhabi for the FIFA Club World Cup 2009 next week, meet city rivals Espanyol and will be hoping to extend their advantage at the top. Over in the capital, the disappointed meet the forlorn when Atletico Madrid host Villarreal, not the top-of-the-table encounter the clubs imagined before the season, but a meeting between fallen giants struggling for mid-table respectability.

The question: Gonzalo Higuain turned 22 on Thursday. Will the Argentinian forward receive a late birthday present in the form of three points and perhaps a goal for Real against Valencia?
The big game: Valencia–Real Madrid, Saturday, 22.00, Mestalla
The quote:
"We’re without David Silva, but we’re not making a fuss about it, although he’s just as good as them [Cristiano Ronaldo and the injured Kaka] and plays in a similar position," David Albelda, Valencia midfielder

Serie A: Cassano takes on former employers
Weekend opponents Sampdoria and Roma are currently level on points, but the match has special significance for the former's mercurial forward Antonio Cassano, desperate to score against his ex-club and help his current one move back above their sixth-placed rivals. The men from Liguria urgently need a win in any case, as two 3-0 defeats on the spin have threatened to derail a promising campaign.

The top three face manageable tasks on paper. Inter Milan coach Jose Mourinho is banished to the stands for the leaders’ visit to Atalanta, but if he so wished, he could swap notes with opposite number Antonio Conte, who is also banned from the touchline. AC Milan entertain Palermo and Juventus, smarting from a 4-1 home loss to Bayern Munich in midweek, visit promoted Bari.

The question: Juve beat Inter 2-1 last weekend, but suffered their worst-ever Champions League home defeat to Bayern on Tuesday. How will I Bianconeri react?
The big game: Sampdoria–Roma, Sunday, 20.45, Luigi Ferraris
The quote: "If there’s no passion, we’re just an ordinary team, and not the great team we basically should be. But we’re Juventus, so we have to bounce back," Fabio Cannavaro, Juventus defender

Ligue 1: Lyon at the crossroads
The evidence suggests former serial champions Lyon are seriously on the wane. The side in fourth could silence the critics at a stroke by beating the very team who toppled them from the throne after a run of seven title triumphs on the bounce. Indeed, Lyon’s meeting with leaders Bordeaux is a must-win affair for the home team, as the gap to Yoann Gourcuff and Co is already five points. The omens are not great, as OL have failed to win on home turf since late September.

In that match, Lyon beat Toulouse, who entertain fellow southerners Montpellier in the 16th round. The promoted outfit are the surprise package of the season, lying second with a game in hand on the leaders, who they meet in a rearranged fixture next Wednesday. In the capital, Paris Saint-Germain face increasingly troubled Saint-Etienne.

The question: Can Lyon turn the corner against bitter rivals Bordeaux and spare coach Claude Puel the inevitable calls for his head?
The big game: Lyon–Bordeaux, Sunday, 21.00, Stade Gerland
The quote: "There is no crisis in Lyon!" Jean-Michel Aulas, Lyon chairman

Bundesliga: Emotional reunion for Ozil
Over the last few months, highly-rated Werder Bremen and Germany starlet Mesut Ozil has given off all the signs of embarking on a glorious career. The 21-year-old, born to Turkish parents in Gelsenkirchen, made his professional debut for his hometown club Schalke. Second-placed Werder now host the third-placed Royal Blues, when Ozil will set aside former friendships for 90 minutes in the effort to close the gap to leaders Bayer Leverkusen.

However, it would come as a surprise if undefeated Bayer were to drop points this weekend, as Jupp Heynckes’ high-flyers visit bottom club Hertha Berlin, who have won just once this term. Elsewhere, Bayern will be looking to build on their thumping success over Juventus when they travel to relegation-threatened Bochum, while injury-ridden Hamburg make the trip to second-bottom Nuremberg desperate for points to stay in touch with the leading group.

The question: Can champions Wolfsburg bounce back from a midweek Champions League exit when they host Borussia Dortmund?
The big game: Werder Bremen–Schalke, Saturday, 18.30, Weserstadion
The quote: "We’re a young team, but we’re very mature. We’ve stopped just charging forward all the time," Stefan Kiessling, Bayer Leverkusen striker

In the Netherlands, Dick Advocaat squares up to a challenging debut. The Belgium coach took a second job at the helm of champions AZ this week, and opens his reign away to second-placed PSV, where he was in charge from 1995 to 1998.

According to the form book in Greece, there can only be one result when tail-enders Panthrakikos travel to undefeated leaders Olympiakos. No better place or time for the minnows to record a first win of term, perhaps?