Barcelona will play Ronald Araujo as a makeshift right back to contain Manchester United's Marcus Rashford.
The Red Devils are set to visit the Nou Camp on Thursday in the first leg of the Europa League, with the return at Old Trafford seven days later.
Xavi Hernandez has used the same tactical plan in recent El Clasico fixtures to effectively subdue Real Madrid's Vinicius Jr.
The Uruguayan, 23, who usually starts as a centre-back for the La Liga club, is expected to be positioned in a similar way, according to Diario AS.