Lewandowski suffered a back injury in Sunday's 1-0 defeat at Real Sociedad during which he had a goal controversially disallowed.
Lewandowski's early disallowed strike led to furious debate over whether the Polish forward had been offside or not.
Barcelona coach Hansi Flick said he thought playmaker Dani Olmo would be ready despite feeling unwell overnight, while defender Pau Cubarsi can play despite suffering a cut on his face during the team's Champions League win over Red Star Belgrade on Wednesday.
It was another commanding victory for LaLiga leaders Barcelona who are in an imperious vein of form, scoring 24 goals in six successive wins in all competitions, including thrashings of Bayern Munich and Real Madrid.
Dani Olmo struck twice for Barcelona on his first start after an injury absence as they beat local rivals Espanyol 3-1 on Sunday to move nine points clear at the top of La Liga.
"Honestly I don't see it as extraordinary, even if some people do... when I was little I also looked on from the outside, watching from my house seeing Messi lift Ballons d'Or and thinking it was incredible. Once you are on the inside, you take it normally, naturally, although if I stop to think about it, it's something really big."
The Catalan giants triumphed at the Santiago Bernabeu to snap Madrid's run of 42 matches unbeaten and continue their own revival under the German coach who arrived this summer.
Defending champions Real Madrid are set to host archrivals Barcelona in a LaLiga game at the Santiago Bernabeu tonight.
Kylian Mbappe's start at Real Madrid has been satisfactory, his performances neither spectacular nor underwhelming, but Saturday's La Liga Clasico offers the French superstar a springboard to kick on from.
Signed earlier in the summer from RB Leipzig after playing a central role in Spain's Euro 2024 triumph, the 26-year-old Olmo had to wait two games until Barca could register him due to LaLiga's strict financial control rules.
A late goal by new signing Dani Olmo gave Barcelona a nervy 2-1 comeback victory at Rayo Vallecano on Tuesday, as the LaLiga leaders continued their perfect start to the season with a third consecutive win.
Barcelona were finally able to register new signing Dani Olmo with La Liga on Tuesday and he is expected to make his debut later on against Rayo Vallecano.
"I know Robert (Lewandowski) really well and I don't think he has returned to form because that's how I have always seen him as a player," Flick told DAZN.
The German coach celebrated his first competitive match at the helm with three points as Barca came from behind against Ruben Baraja's solid Valencia side.
Four people have been arrested after a knife attack on the father of young Spanish football star Lamine Yamal in Catalonia, local police told AFP Thursday.
The 2024/25 La Liga campaign kicks off tonight, with Athletic Club hosting Getafe at 11:00 pm (Bangladesh Time) and Girona facing Real Betis away from home at 1:30 am (Bangladesh Time) on Friday.
After a summer dominated by Spain, with La Roja storming to Euro 2024 triumph and their youngsters claiming gold at the Paris Olympics, the focus now turns to Spain once again as LaLiga kicks off on Thursday.
Barcelona confirmed on Sunday captain Sergi Roberto has left the club after 14 seasons with the Catalan giants.
RB Leipzig's Spain international Dani Olmo is leaving after more than four years at the Bundesliga club, the midfielder said on Friday, and is now expected to join Barcelona.