Coached by Argentine Eduardo Berizzo, Celta inflicted the biggest La Liga defeat on Barca, excluding games against Real, in more than a decade last month.
Celta and Real are the only two unbeaten teams in the league and the sides are level on 18 points with Barca, who host Eibar on Sunday, after eight matches.
Atletico Madrid are two points behind in fourth before Sunday's game at home to Valencia, with fifth-placed Villarreal also on 16 points before they play at promoted Las Palmas on Sunday.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Real have been without several injured regulars in recent games including Gareth Bale, Karim Benzema, Luka Modric and James Rodriguez, and Celta goalkeeper Sergio Alvarez believes his side have a great chance to secure home wins over both of Spain's dominant pair in the same season.
"We are on good form but Real Madrid have players who can change the game at any moment," Alvarez told a news conference on Wednesday.
"I don't think they are that much better because we are very good and we are working very well," he added.
"We will have to control the game because they have some very dangerous moves. It will be vital to avoid losing the ball in midfield."
Sevilla will look to rebound from Wednesday's 2-1 Champions League defeat at Manchester City when they host Getafe on Saturday.
The Europa League holders are, at the very least, expected to be challenging for the Champions League qualifying places this season but have started poorly in La Liga and are stuck down in 13th on nine points.
Captain Jorge Andujar said Sevilla's performance at City, where they took the lead but were eventually undone by a 91st-minute Kevin De Bruyne winner, was proof of their potential.
"You come away angry because you have played a great game," he told reporters. "We can see that the team is making progress."
(Editing by Peter Rutherford)
