Barca could be five points adrift of Real by the time they kick off as the European champions host Leganes on Sunday.
Madrid endured an embarrassing night in front of an empty stadium on Wednesday as they spurned a two-goal lead to draw 3-3 away at Legia Warsaw.
The match was played behind closed doors due to violence and racist chanting from Legia fans.
Yet, only Mateo Kovacic’s equaliser five minutes from time allowed Madrid to extend their unbeaten run to 27 games, and coach Zinedine Zidane once again criticised his side’s lack of intensity.
“We lacked intensity, desire and movement,” said the Frenchman.
“At times you can have these odd games and we’ve got to be patient. The good thing is that we didn’t lose and we’re now focusing on our next game.”
Madrid could be boosted by the return of Luka Modric for the first time in a month after he underwent surgery on a knee cartilage problem.
Marcelo and James Rodriguez should also be fit after missing the trip to Warsaw, but Sergio Ramos, Casemiro and Pepe remain sidelined.
It is the first time Leganes have ever faced Real in league action.
After a bright start to their debut La Liga campaign, three consecutive defeats have seen Leganes, nicknamed the ‘cucumber growers’, slip to a point above the relegation zone.
Atletico Madrid are three points back on Real in third, but can move top when they travel to Real Sociedad on Saturday.
Diego Simeone’s men were the only Spanish side to book their place in the last 16 of the Champions League in midweek, but needed a dramatic 93rd-minute Antoine Griezmann winner to see off FC Rostov 2-1.
Centre-back Stefan Savic is suspended with Lucas Hernandez or the fit-against Jose Maria Gimenez set to deputise.
Kevin Gameiro should also replace Fernando Torres in attack.
Real Betis coach Gustavo Poyet’s job is on the line when his side visit fifth-placed Villarreal on Sunday.
Betis are just two points off the relegation zone in 13th and fans called for Poyet’s head during last weekend’s 1-0 defeat at home to Espanyol.
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