Hart's comments come after he recently restricted Barcelona to just one goal during their Champions League clash at the Nou Camp. Despite having saved shot after shot from Barca's attacking trio of Messi, Neymar and Luis Suarez, Hart said that stopping Aguero from scoring on a daily basis is a much tougher challenge.
"Messi is absolutely awesome, but I'm backing Sergio because he's my player," Hart said at a press conference ahead of England's Euro 2016 qualifier against Lithuania. "Just working with him on a daily basis and, from what I've seen this season, the best is probably Aguero. He just knows how to score.
"We've got a good team, but in training he excites you most days and he's also got that ability on the day to do it. He's got the skill to turn a long clearance into a goal because he's got that ability to take it round five people and score. It's a great thing to have.
"Sergio is a very natural player and in a one-on-one situation there is nothing complicated about it. He takes that option to score."
Hart explained that his confidence has skyrocketed as a result of his sensational performance against Barcelona..
"Yes, definitely," he said. "It was a good night for me personally, making saves against some of the best players in the world.
"You've got to believe in what you're doing, be strong in what you do and stuff like that [performance against Barca] isn't going to harm it.
"They [Messi and Suarez] are human beings and appreciate that I was making a lot of good saves."