The 25-year-old, who last featured for the Black Stars in 2017, believes he has done enough to earn a comeback to the team for the 2019 Africa Cup of Nations qualifier against Sierra Leone next month.
"It hurts that I have been ignored, because everyone wants to play international football," Duncan told KweseESPN.
"It is a compliment to be considered good enough for your country, and all I can personally do is to make my case by playing well at club level which I've been excellent this season," he added.
"Normally, in the past, I play two good games and then my level drops the next," he said
"This time, the level has been consistent and every day I feel better about myself. I get more minutes on the pitch which works magic for any player."
"Going out on loan gave me an unbelievable experience. At Inter, I benefitted from training and playing with some of the biggest names and internationals from all over the world.
"Then, when I went on loan, I learnt to graft and work extremely hard. It has shaped me well at Sassuolo so far.
"I have acquired a lot of experience from being here. I am better equipped at dealing with people and I think I have also grown as a footballer because the football here is so good, you are forced to think on your feet."
"By the end of the season, I want to have helped Sassuolo qualify for the Champions League and prove to everyone just how good I am.
"I just want to improve in every way, as much as I can."
Duncan boasts of nine international appearances and one goal for Ghana after making his debut in 2012 against Cape Verde.