The Catalans have not won the Spanish title since Ernesto Valverde was at the helm in 2019 and expanding the gap on their bitter rivals in second would virtually clinch it.
Madrid won the first La Liga Clasico 3-1 in October but Xavi's side have vastly improved since then.
The coach is desperate to win the league title to validate the team's growth, while for the club it would represent a swift return on their outlay last summer.
Despite their financial crisis, Barcelona signed Robert Lewandowski, Jules Kounde, Raphinha and other players by selling off future television rights in a move some blasted for gambling with the club's future.
Champions League group-stage elimination, followed by a Europa League knock-out by Manchester United, confirmed Barcelona still have a long way to go, but they have made significant progress.
Beating Real Madrid 3-1 in the Spanish Super Cup final in January in Saudi Arabia earned Xavi his first trophy as coach, and the performance was dominant.
By contrast, when the teams met earlier March in the Copa del Rey semi-final first leg, Madrid had the better of the game, but Barcelona still scraped a 1-0 win.
How the Catalans approach this Clasico is a key issue for Xavi to decide.
Fans at Camp Nou may not react well to a similarly defensive performance, and will expect Barcelona to take the initiative more.
That will be significantly easier if midfield maestro Pedri is fit.
Without the Canary Islander, already essential for club and country at 20 years old, Barcelona seem virtually incapable of playing possession football.
Pedri has been missing with a thigh injury for six games across all competitions and in his absence, when Barcelona have won it has been by relying on their rock-solid defence.
Karim Benzema and Vinicius Junior fired blanks at the Santiago Bernabeu in the Copa Clasico and the latter has been shackled by Ronald Araujo in recent battles with Barcelona.
Xavi tends to select the Uruguayan centre-back at right-back against Madrid so he can face off against the Brazilian winger.
Barcelona have found that by shutting down Vinicius, Madrid's attack is significantly less dangerous.
"For me he is the best in the world," said Madrid coach Carlo Ancelotti after the Champions League win over Liverpool in midweek, backing Vinicius to the hilt.
However Madrid may need to prove they have other routes to goal if Vinicius is kept quiet.
The winger set up Benzema as Los Blancos beat Liverpool 1-0 on Wednesday to reach the Champions League quarter-finals, 6-2 on aggregate.
It was a strong display which shows the reigning Spanish and European champions can produce the goods when it truly matters to them.
The opportunity to cut the gap on Barcelona to six points at the top of La Liga could re-ignite the title race, but the record 14-time European champions' main goal is retaining that trophy.
"We have to continue with this rhythm, playing like we've played today, and I hope it's like that in the Clasico, we have to win," said Madrid goalkeeper Thibaut Courtois, after beating Liverpool.
Benzema is expected to be fit after taking a blow to the shin against the Reds, but Barcelona are still missing his compatriot Ousmane Dembele.
To upset the Catalans, Madrid will have to manage something only one other La Liga side have accomplished all season -- scoring against the hosts at Camp Nou.
Joselu netted a penalty for Espanyol in December and no player has scored from open play in the top flight this season at Barcelona's stadium.
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