The Blaugrana name a makeshift defence for their clash in the Spanish capital as they continue to deal with the absences of Gerard Pique and Carlos Puyol
Javier Mascherano is suspended for this match following his red card against Deportivo last weekend, with Adriano filling in alongside Song tonight as Gerard Pique and Carlos Puyol remain sidelined through injury.
Elsewhere, Martin Montoya comes in at right-back for the Liga leaders, while Cesc Fabregas is preferred to Andres Iniesta in midfield. Upfront, Alexis Sanchez is replaced by David Villa.
Rayo have also made changes for tonight's game, with Jordi Amat returning from injury to take his place in the centre of their defence alongside Rodri, who is replacing the suspended Mikel Labaka following the defender's dismissal against Espanyol in last week's 3-2 defeat.
The Madrid-based side line up in a more defensive formation as they name three central midfielders as opposed to their normal two, with Paco Jemez setting his team up in a 4-3-1-2 rather than their usual 4-2-3-1.
Rayo Vallecano (4-3-1-2): Ruben; Tito, Rodri, Amat, Casado; Javi Fuego, Leo, Chori; Jose Carlos; Delibasic, Piti
Subs: Dani, Galvez, Gonzalez, Trashorras, Vazquez, Bille, Lass
Barcelona (4-3-3): Valdes; Montoya, Song, Adriano, Alba; Xavi, Busquets, Cesc; Pedro, Messi, Villa
Subs: Pinto, Alves, Bartra, Dos Santos, Iniesta, Tello, Alexis