The Inter striker will miss the team's next Serie A match against Cremonese, according to Sky Sport Italia.
The 29-year-old footballer suffered a thigh injury during today's training session. The Belgian will undergo a medical in the near future but is not expected to help the Nerazzurri against Cremonese on Tuesday. Rommel's participation in the Milan derby on Saturday is also in doubt.
Since his return to Giuseppe Meazza, Lukaku has scored one goal in the opening three rounds of the new Serie A season.