But Lionel Messi is fit again and will be in Barcelona’s squad for the Group F showdown at Camp Nou.
Lukaku has been on form since leaving Manchester United for Inter in a £73million summer switch, with his three goals so far making him joint leading goalscorer for the Serie A leaders along with midfielder Stefano Sensi.
But Inter boss Antonio Conte confirmed on Tuesday the striker will miss Wednesday’s clash.
“Romelu didn’t travel with us because he’s got a slight problem with his quadriceps,” Conte said.
“It’s a problem he’s had for about 10 days now and one that he kept on mentioning, but tests have revealed that it’s nothing serious.
“We’re quite relaxed about it but didn’t want to risk him.”
Inter have a 100% record in Serie A after six games and host second-placed Juventus on Sunday.
And Conte said he does not know yet whether Lukaku will be fit for the top-of-the-table clash.
“It’s not a tear, so we are fairly relaxed and will focus on that only after tomorrow’s game with Barcelona,” Conte added.
Meanwhile, Barcelona coach Ernesto Valverde named Lionel Messi and Ousmane Dembele in his squad for Wednesday’s match, with both forwards declared fit after they took part in training on Tuesday.
Messi limped off during Barca’s 2-1 win over Villarreal last week after suffering an adductor injury while Dembele has been nursing a thigh problem.
However, Barcelona will be without full back Jordi Alba, centre back Samuel Umtiti and 16-year-old winger Ansu Fati.
All four teams in Group F have one point, with Barca having drawn 0-0 at Borussia Dortmund in their opener while Inter drew 1-1 at Slavia Prague.