Nainggolan has now announced his international retirement.
"I wanted to be there, of course, but he made his choice, even if I'm still not entirely clear on the reasoning behind it," Nainggolan told VTM Nieuws.
“Not playing the World Cup was a heavy blow, especially as I had already missed one. I have been at Roma for four years and played four very good seasons.
“I think I deserved a bit more respect with my performances."
He was asked about the fan protests, with plans to stay silent during the first 15 minutes of their next friendly.
“It's nice to receive support and respect from the people and my teammates, but now we must all concentrate on the team. There's a World Cup to play and I hope we can go as far as possible."