Radja Nainggolan says "the door is always open" for a return to Roma as he revealed his pain at leaving for Inter.

Former Belgium international Nainggolan joined Roma from Cagliari in 2014, establishing himself as a star performer in the capital before his exit in 2018.

The 31-year-old is back at Cagliari on loan after subsequently falling out of favour at San Siro and a future return to another of his former clubs also appeals.

"I would go back to Roma. If the conditions are right, I would go back," Nainggolan told Er Faina on Instagram. "The door is always open.

"I lived beautiful years there, where they love me, where I always gave everything."

Despite choosing to join Inter nearly two years ago, Nainggolan explained it hurt to leave Roma.

Coach Luciano Spalletti was then sacked in May 2019, and the midfielder was pushed out of the door under Antonio Conte.

"It was my choice to go to Inter," Nainggolan said. "They had Spalletti, with whom I had a good time at Roma. My choice was easy. Spalletti, for me, is the best coach I have ever had.

"But if you asked me if I was happier to have arrived at Inter or sadder to have left Roma, I would have told you the latter.

"Maybe I wasn't myself, maybe a little because of guilt or maybe other things. I can't explain it. I could give more.

"Then Inter dumped me, even though I went to China on tour. I already knew that I would not play the friendlies, but I left the same."