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.
Young Barcelona midfielder Fermin Lopez struck twice to secure his team a hard-fought 2-0 win at Almeria on Thursday in La Liga.
Xavi Hernandez's side leapfrogged Girona to move on to 76 points, one clear of their Catalan rivals who dropped points in Friday's 2-2 draw at Alaves.
If anything defines Real Madrid it is a relentless hunger for silverware and that remained clear even as they celebrated their 36th La Liga title triumph on Sunday.
Real Madrid claimed a record-extending 36th LaLiga title on Saturday after Girona's 4-2 thrashing of local rivals Barcelona left Carlo Ancelotti's side with an unassailable lead in the standings.
"We will keep fighting and next season we have to change a huge amount of things," said Xavi.
The club, in La Liga for only the fourth season in their history, beat Barcelona 4-2 at their tiny Montilivi stadium to secure a top four finish.
Carlo Ancelotti's side romped clear of last season's winners and shock challengers Girona to clinch their record-extending 36th La Liga trophy
Real Madrid, who have lost only once in the league this season, hold a 13-point advantage over second-placed Girona while Barcelona dropped to third
Real Madrid earned a comfortable 3-0 win over Cadiz which ensures they will win La Liga if Barcelona fail to beat Girona later Saturday.
Barcelona will be favourites when they visit Girona on Saturday but the hosts are ready to seize a historic opportunity to beat them in front of their own fans, Girona manager Michel said on Friday.