Lionel Messi struck his 500th Barcelona goal with nearly the last kick of the game to blow the La Liga title race wide open with a thrilling 3-2 win at Real Madrid on Sunday.
"With the Appeal Committee (Spanish federation) dismissing FC Barcelona's appeal for the three-match suspension of Neymar Jr, the club will appeal the decision to the Court of Arbitration for Sport (in Spain)", Barcelona said in a statement.
The last time Messi did score in El Clasico, he grabbed all three in a 4-3 win - another hat-trick would do nicely on Sunday.
In that game, Sergio Ramos scored the equaliser late and that gave the Los Blancos a valuable point after a solid performance.
Meanwhile, this is a must win game for Barcelona if they want to stay in the title race.
The contest was typically controversial, Cristiano Ronaldo having a strong early penalty claim turned down, while Barca wanted Casemiro's opener chalked off as they claimed for offside against Ramos in the build-up, a goal that was promptly cancelled out by Messi before half-time.
They're now sitting three points behind Real Madrid, but Zinedine Zidane's team also have a game in hand.
The Zinedine Zidane - tutored side were held to a draw by Atletico in their last home fixture, but they have won eight of their last 10 games in all competitions and drawn the other two. The Argentine now holds the record for the most goals in an El Clasico match with 21 while Cristiano Ronaldo has 16.
Messi has been more than comfortable when playing at the Bernabeu, where he has 12 career goals. "He's on the verge of 500 goals for the club and my pass set up the first of them", Ronaldinho said. "We'll take it game by game because every single one is crucial".
The visitors will be without superstar Neymar, who is serving a suspension. Madrid, seeking its first league title since 2012, also has a game in hand.
The Catalans have gone through a hard period recently, losing two of their last four games across all competitions, including a 2-0 defeat away at Malaga in La Liga.
Gareth Bale is a doubt for the match but should start, which may be a relief, the Welshman has struggled to find his best form since returning from a long lay-off, while Isco has thrived in recent weeks.