The Belgian forward signed last summer but found playing time hard to come by under both Villas Boas and his replacement Roberto di Matteo.
Lukaku told Sportwereld: “There is one person that I will never forgive for what he did to me – the previous coach. It’s not just that. It was also the way he spoke to me and treated me.
“Right from the beginning, it was weird. I could not stand how he was treating me. I received no explanation. In training, he put me on the right or left wing. In training matches, I was a substitute with a shirt to keep swapping teams. I really learned nothing.”