Cristiano Ronaldo and Lionel Messi meet on Sunday when Real Madrid and Barcelona play their latest Clasico.
The outcome at Santiago Bernabeu Stadium could allow Madrid to virtually secure its first league title since 2012, or put Barcelona back in position to win its third consecutive trophy.
A home victory would give Ronaldo's Madrid a three-point lead with five rounds to go and a game in hand. A win by Messi's Barcelona would open up the title race and put the club back in the lead on the head-to-head tiebreaker.
"The world grinds to a halt to watch this game," Madrid left back Marcelo said. "It is huge, every player wants to play it, and people have been talking about it for the past month."
Ronaldo and Messi, the only players voted best in the world over the last nine years, have thrived in Clasicos, and enter this one in top form.
Ronaldo has 12 goals in his last 11 matches for club and country, including five goals in the two legs against Bayern Munich in the Champions League quarterfinals.
Messi wasn't able to help Barcelona overturn its three-goal deficit against Juventus in the last eight of the Champions League, but he has been having one of his best seasons for the club. He has 45 goals in 45 games in all competitions, including six in his last six games. Messi is La Liga's leading scorer with 29, five more than teammate Luis Suarez.
Messi has the habit of being decisive when facing Madrid. He has 21 goals in 33 games against the rival, the most in the history of the Clasico.
Ronaldo has 16 goals in 26 matches between the clubs, the third-best mark behind Messi and Madrid great Alfredo Di Stefano.
Messi has been more than comfortable when playing at the Bernabeu, where he has 12 career goals. The only stadium where he has scored more, other than the Camp Nou, is at Atletico Madrid's Vicente Calderon.
One of Messi's most impressive performances against Madrid came when he netted a hat trick in a 4-3 league victory in the 2013-14 season. He also had a pair in a 2-0 win in the semifinals of the Champions League in 2011.
If he scores twice again on Sunday, Messi will reach his 500th goal in official matches with Barcelona. He would be the first player to reach that mark with the club.
Barcelona has won two of the last three games against Madrid at the Bernabeu, including 4-0 in the league two seasons ago.
Madrid enters this Clasico in much better form, having won six of its last seven league games. The only setback was a 1-1 home draw against city rival Atletico Madrid two rounds ago.
Barcelona has won only two of its last five games in all competitions, with losses to Juventus in the Champions League and Malaga in La Liga.
Barcelona will be without the suspended Neymar, while Madrid is expected to welcome the return of Gareth Bale from injury.
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