Swansea winger Sinclair is on the brink of a call-up for the England under-21 squad after destroying npower League One Peterborough with his first professional hat-trick.
Sinclair, who cost City £500,000 from Chelsea, earned the Swans a place in the fourth round of the Carling Cup thanks to three clinical strikes at London Road.
His recent performances and his treble in their 3-1 win have put him on the check list of England under-21 boss Stuart Pearce.
"I contacted Stuart and asked if Scott was on their radar," confirmed Swans boss Brendan Rodgers. "To be fair to Stuart, he told me they had been hearing all about him and the scouts had been watching him.
"He is still blossoming. He gets better with games and is really maturing. There is still a lot to come from him. He is still developing. Every game he plays, it looks like he is going to score. He knows he has got a lot to learn but he is a good kid.
"I know the boy well and his mentality. We kept in touch when I left Chelsea. He was a big talent when he broke on the scene at 17 but then went out on loan at teams where he did not play. When you get to 20 or 21, you need to go. Scott's career was out on loan at clubs in difficult moments. He was not getting the game time.
"He needed to find a home. I spent hours on the phone to him and convinced Swansea was the place for him to be. He can help the club and help himself. He has had two years resting. He is so fresh, he wants to play every game. He wants to score goals and at this moment in time in his career, he will tell you, he wants to play football. He is loving it at Swansea."