Sterling has emerged this season as one of the best players in the Premier League.
And former City keeper Hart recalled when Sterling arrived from Liverpool, telling Sky Sports: “He was an amazingly talented footballer when he came.
"He came under a lot of pressure from Liverpool. He was a bit hit-and-miss under Manuel Pellegrini. He played in positions that he felt were not his strongest, but this manager has got the best out of him. His confidence is high.
"There were always flashes of his excellent finishing, but speaking to Richard White, the coach at City, he doesn't miss now. Top player."
He added: “He's shown a maturity both on and off the pitch this season. He's the first name on the team-sheet.
“He's rapid, direct, brave and strong. He's scoring goals and is on fire. He's improved. He's going to get better and better. He's been fabulous.
"Okay, he's had to deal with some nonsense on the pitch, but he's dealt with that like a very experienced footballer and human being."