Rome - Belgium forward Romelu Lukaku said in an interview published on Thursday he is "not happy" at Chelsea after starting just eight league games this term.
Blues coach Thomas Tuchel has preferred a formation without the 28-year-old, who has suffered from injury and Covid-19 this season.
Lukaku joined the English side in August after winning Serie A with Inter Milan earlier this year.
"After two years in Italy, in which I worked a lot at Inter with trainers and nutritionists, I am physically fine," Lukaku told Sky Sport Italia.
"But I'm not happy with the situation, this is normal. I think the coach has chosen to play with another system, I just have to not give up and continue to work and be a professional.
Romelu Lukaku to @SkySport: "Physically I am fine. But I'm NOT happy with the situation at Chelsea. Tuchel has chosen to play with another system - I won't give up, I'll be professional. I am not happy with the situation but I am professional - and I can't give up now". 🔵 #CFC pic.twitter.com/KGNoJ10cwp— Fabrizio Romano (@FabrizioRomano) December 30, 2021
"I am not happy with the situation, but I am a worker and I must not give up," he added.
Lukaku made 10 assists and scored 24 times in the league as Inter claimed the Scudetto for the first time since 2010.
Chelsea paid £97.5 million ($131 million) for the ex-Manchester United attacker, who spent three seasons at Stamford Bridge earlier in his career.
"How I left Inter, how I communicated with the fans, this bothers me because it is not the right time now, but even when I left it was not the right time," Lukaku said in the interview which reportedly took place three weeks ago.
"Now I think it is right to speak because I have always said that I have Inter in my heart, I will return to play there, I really hope so.
"I am in love with Italy, this is rightly the time to talk and let people know what really happened without talking badly about people because I am not like that.
"I want to say a big apology to the Inter fans because I think the way I left should have been different.
"I really hope in the depths of my heart to return to Inter, not at the end of my career, but at a still good level to hopefully win more."
Lukaku scored his ninth goal of the season in Wednesday's draw with Brighton before Chelsea head to third-placed Liverpool on Sunday.