With just four weeks to go in western Europe's top leagues, wins and defeats now can prove doubly crucial when the points are finally totted up in May. El Clásico in Spain is far and away the marquee fixture this weekend, but the contenders in England, Italy, France and Germany all also face stern tests of their credentials.

FIFA.com previews the weekend action in Europe’s five biggest leagues.

Premier League: Do-or-die time for wounded United
The lack of an English club in the UEFA Champions League semi-finals for the first time in seven years prompted a brief bout of soul-searching during the week, but that will be pushed to the back seat at the weekend by the potentially thrilling action in both big domestic competitions.

Champions Manchester United can do their bruised morale no end of good by returning to the top of the Premier League with a win over Blackburn Rovers. Chelsea cannot respond immediately in the league, as the London side are busy with the FA Cup semi-final against Aston Villa. The second last four clash in the cup sees Tottenham Hotspur take on Portsmouth. Due to Spurs’ appointment at Wembley, Arsenal have the weekend off.

The question: After last weekend’s devastating 2-1 home defeat to Chelsea and the midweek Champions League exit at Bayern’s hands, can United return to winning ways against Blackburn?
The big game: Blackburn Rovers-Manchester United, Sunday, 14:30, Ewood Park
The quote: "Fighting back is in the nature of this club, and a big part of our history," Manchester United manager Sir Alex Ferguson.

La Liga: The greatest showdown of them all
The pivotal moment in the Spanish title race has arrived. And for all the predictability of the big two’s dominance in the league, nothing comes close to the sense of global anticipation ahead of a Real Madrid-Barcelona showdown.  On this occasion, the teams are level on points, with Real ahead of the champions on goal difference. The men from Madrid have home advantage, but he Catalans have Lionel Messi, whose stellar displays of late have prompted an avalanche of superlatives from commentators, pundits and fans everywhere.

With the world at large glued to events at the Bernabeu, third-placed Valencia will go about the business of amassing points towards a direct qualifying spot for the Champions League. David Villa and Co face a tough test away to fifth-placed Mallorca, who have won 12 of their 14 home games this term.

The question: Last season, Real crashed 6-2 at home to the FIFA Club world champions. Can Cristiano Ronaldo and friends take revenge?
The big game: Real Madrid-Barcelona, Saturday, 22:00, Estadio Bernabeu
The quote: "I’m taller and broader than Messi. But seriously, he’s having a terrific season, and he’ll always go down as one of the greats, although let’s not overlook the contribution made by his coach and team-mates," Real Madrid forward Cristiano Ronaldo.

Serie A: Must-win meeting for Juventus
Twelve league defeats so far and seventh place in the standings is not exactly what Juventus and their fans expected this season. The Turin giants are in a rut, sustained only by the memory of past glories and titles. One piece of good news for beleaguered coach Alberto Zaccheroni is the return from injury of keeper Gianluigi Buffon for Sunday’s home meeting with Cagliari. Juve must win to keep alive any hopes of qualifying for the Champions League.

At the top of the standings, the three-way tussle for the title goes into its next exciting round. Leaders Inter appear to have the toughest task on paper with the trip to Fiorentina. Roma, just a point off the champions, visit relegation-threatened Atalanta. AC Milan entertain Catania with reasonable hopes of cutting the three-point gap to their bitter rivals from across town. Elsewhere, the Derby della Lanterna sees Sampdoria take on Genoa.

The question: Roma’s most recent league defeat, a 2-1 reverse against Udinese, was in late-October last year. Can the men from the capital maintain their sparkling form?
The big game: Fiorentina-Inter, Saturday, 20:45, Artemio Franchi
The quote: "We need to be very careful indeed in the domestic championship, because losing it now would be horrendous," Inter President Massimo Moratti.

Ligue 1: Lyon on a roll
After racking up seven domestic league titles on the bounce, Lyon finally relinquished the French crown to Bordeaux last season, and an era appeared to be at an end. Yet Claude Puel’s side have been enjoying a rich vein of form of late, culminating in a place in the Champions League semi-finals and second place in Ligue 1. This weekend OL entertain sixth-placed Lille, and will be only too keen to pile the pressure on their rivals.

In the closest and most exciting run-in for years, with just three points separating sixth from first, Marseille have moved to the top, but have played a game more than Bordeaux. OM are at home to Nice, with Les Girondins on the road to Paris Saint-Germain. After two winless fixtures, Montpellier will hope to recapture the winning habit away to Le Mans.

The question: Montpellier have only won one of their last five matches. Are the promoted club running out of steam with the finishing line in sight?
The big game: Lyon-Lille, Sunday, 17:00, Stade Gerland
The quote: "Leading the league is great, but we have all kind of obstacles to overcome yet," Marseille coach Didier Deschamps.

Bundesliga: Can Bayern be stopped?
A couple of weeks ago, Bayern Munich were the first to admit that their upcoming fixtures could make or break their season. Munich duly beat Schalke to seal a berth in the cup final, beat them again to go top of the table, and knocked Manchester United out of the Champions League. Louis van Gaal and his men now tackle the last part of their punishing spring programme, the trip to third-placed  Bayer Leverkusen, who comfortably led the league for a long period until their customary March implosion. Franck Ribery, Arjen Robben and Co will fancy their chances of at least maintaining their lead in the standings.

Schalke remain just a point off Bayern and will be hopeful of victory away to crisis club Hannover. At the very bottom of the table, there appears to be a minor miracle in the making. Hertha Berlin looked doomed at the midpoint of the campaign, but are now only three points off a relegation play-off spot. Victory over Stuttgart on Saturday would nourish their hopes even further.

The question: Leverkusen have lost their last three in the league. Can they bounce back against leaders Bayern?
The big game: Leverkusen-Bayern, Saturday, 18:30, BayArena
The quote: "We don’t have the time to start dreaming. We’ve won absolutely nothing yet," Bayern captain Mark van Bommel.

Two of Europe’s great cities stage prestigous and history-laden derby clashes this weekend. In Portugal, Lisbon rivals Benfica and Sporting cross swords, while fans in the Czech Republic are looking forward to a showdown in Prague between Sparta and Slavia. Benfica and Sparta will enjoy home advantage and lead their respective championships, so wins would represent significant progress towards the title.