Sources have told Goal that Lucas Vazquez is set to be handed a supporting role on the opposite flank to Vinicius, with in-form Karim Benzema leading the line at the tip of the attack.
That would mean that Marco Asensio, who, like Bale, has been struggling with injuries this term, will also have to settle for a place on the bench, while January signing from Manchester City Brahim Diaz isn't part of the travelling squad.
Vinicius has emerged as a key part of Santiago Solari's first team since he took over, starting the last nine games in all competitions having played just 12 minutes for Julen Lopetegui prior to his sacking.
The decision to start Vazquez, meanwhile, points to the Spaniard's defensive work ethic, with a view to nullifying the threat posed by Jordi Alba on Barca's left flank.
Solari has been keen to keep his cards close to his chest in terms of his line-up for the Clasico, and could well make late adjustments, especially given he has not yet informed his squad over who will start the game.
Indeed, Goal understands Solari will conduct a meeting at the team hotel to inform the players of his decisions, prior to their coach trip to Camp Nou later in the afternoon.
There does, however, remain question marks over the manager's preference at left-back, with Marcelo and Reguilon both pushing for a start.
The Brazilian has bags of Clasico experience having joined the club back in 2007, but has seen his place in the starting XI come under threat since Solari's arrival.
The Madrid boss has often selected Reguilon as a direct replacement for Marcelo, with the 22-year-old having started the last four league games in a row.
Marcelo played both legs of the 7-4 aggregate win over Girona in the quarter-final, but it remains to be seen if Solari opts for his league choice at left-back for what will be a significantly tougher test at Camp Nou.
Goal understands that Cup goalkeeper Keylor Navas will continue to replace Thibaut Courtois in goal, and Casemiro is expected to get the nod in a role at the base of the midfield.
From the Barca side of things, all eyes will be on whether Lionel Messi starts the game although the signs look positive, with the Argentine having trained on Tuesday and having been included in the 19-man squad.
The 31-year-old had been nursing a thigh injury from the 2-2 draw with Valencia at the weekend but will undoubtedly be desperate to play a part in the Clasico.