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.
The 20-year-old underwent surgery after suffering the injury in Spain's Euro 2024 qualifying win over Georgia last year, and missed the rest of the season, along with Spain's triumph at the Euros.
Madrid beat Celta Vigo on Saturday to pull level with Hansi Flick's side but Barca swiftly restored their advantage with a stylish and dominant display of attacking football.
Polish goalkeeper Wojciech Szczesny recently reversed his retirement decision to join Barcelona, but he is not about to change how he lives his personal life, and that includes smoking.
The 24-year-old will miss Spain's Nations League matches against Denmark on Saturday and Serbia next Tuesday, national team coach Luis de la Fuente confirmed.
The 36-year-old hitman looks far sharper than last season and has 12 goals in 11 games across all competitions.
Robert Lewandowski's first-half hat-trick guided LaLiga leaders Barcelona to a 3-0 win away at Deportivo Alaves on Sunday as the Polish striker extended his lead at the top of the league's scoring charts.
Robert Lewandowski struck twice for Barcelona as they demolished Young Boys 5-0 in a one-sided Champions League clash on Tuesday.
Flick is hopeful midfielder Frenkie de Jong can return as Barca look to bounce back after suffering two losses in 10 days, against Monaco in the Champions League and Osasuna in La Liga.
The Catalans won all seven of their opening fixtures but Flick's heavily rotated side came badly undone in Pamplona as Ante Budimir scored a brace either side of Bryan Zaragoza's strike.
The Polish forward struck from close range in the first half to maintain Barca's 100 percent record in the league so far this season with their seventh victory.