Barcelona, March 21 (IANS): At 9 pm local time on Sunday, 98,000 fans at the Camp Nou Stadium here and a worldwide television audience of around one billion will watch what has become the most important club game in the world as FC Barcelona entertain arch-rivals Real Madrid in a game which has become known as 'El Clasico'.

The two biggest sides in Spain will go head to head once again over 90 minutes which will go a long way towards deciding the destination of this season's La Liga title, reports Xinhua.

Barcelona go into the match with a one point lead over Real after slowly clawing their way back from five points down at the start of 2015. A win would lift them four clear of the side who are now their only realistic title rivals.

A win for Real would see them leapfrog back to the top with the destiny of the title firmly in their hands.

As always in this kind of game, all eyes will be on the stars: Lionel Messi, Neymar and Luis Suarez for Barcelona and Cristiano Ronaldo, Karim Benzema and Gareth Bale for Real.

Messi has been on fire and his 32 league goals have seen him overtake an out of sorts Ronaldo as the league's top scorer. Bale had been doubted by the press and fans, but last week saw him score twice to give Madrid a 2-0 win over Levante.

However, the Clasico is about more than the star strikers. And much will depend on how Luka Modric, who is still working back to match-fitness and a tired Tony Kroos can impose themselves on the Barcelona midfield.

The Catalans are still waiting to see if Sergio Busquets can recover from an ankle injury which kept him out of their midweek Champions League tie against Manchester City.

That game means Barcelona have only three days to prepare for the Clasico, whereas Real have had all week. But that is unlikely to be a factor with confidence and will to win bigger factors on the night.

What will be vital is how both defences deal with their rivals' attacking threat and much could depend on Sergio Ramos, who returned to action for Real a week ago.

Ramos should add steel to a Madrid backline which looked shaky without him and put captain and goalkeeper Iker Casillas under pressure.

Casillas was 'rested' last weekend, Madrid coach Carlo Ancelotti now has to make a big decision: does he bring him back for the big game or continue with Keylor Navas, who last week was a virtual spectator against Levante.

Whoever plays will have more work to do on Sunday...and most of the world will be watching.