Today in the 2-0 victory over Chelsea, the England number one denied Frank Lampard from the spot early in the second half and although he admits it was a mistake in bringing down Demba Ba, Mancini was thrilled for Hart to respond with a potentially match-winning save.
"I say to him everything when he did a fault," said Mancini.
"I think we can't concede a penalty like this with a kick (long ball) from 45 metres - he and Kolo (Toure) both did a mistake.
"But after, it was fantastic.
"I think it was important. Maybe the game could have changed, but also if they scored, we would have had another 40 minutes.
"We were playing really well and we could have a chance to score other goals."