Neymar has recovered from his ankle problem and could feature ahead of the Catalans' Champions League clash against Manchester City next week.
The Brazilian sprained his ankle in the Catalans' Copa del Rey clash against Getafe on Jan. 16, but has trained normally over the last few days and is likely to start on the bench for this clash as he builds up his fitness ahead of Barca's trip to Manchester City in the Champions League on Tuesday.
Barca returned to the top of the table last Sunday with a 4-1 win at Sevilla, and remarkably all three leading sides - Barca, Real Madrid, and Atletico - share the same win, draw, loss record.
Gerardo Martino's men suffered a 3-2 defeat against Valencia in their last home game in La Liga, but it would be a major shock if they are unable to beat Paco Jemez's side.
Barca is set to welcome back Carles Puyol after the defender missed the last two games with a back problem.
Javier Mascherano and Jordi Alba played in the 1-1 draw at Real Sociedad on Wednesday and the duo are available to return to duty on Saturday after missing the win at Sevilla due to suspension.
Jonathan dos Santos (knee) is a long-term absentee and third-choice goalkeeper Oier Olazabal (finger) is also sidelined.
Romania fullback Razvan Rat could make his Rayo debut after signing as a free agent on Thursday, having been released by Premier League side West Ham last month.
Jemez has a doubt over Jonathan Viera, while Borja Lopez, Jose Carlos and Seba Fernandez will play no part.