Spieth, who won the Masters earlier this year, knows that he is capable of sealing victory, with the other three joint-leaders all chasing their first major.
"I feel like we (caddie Michael Greller) have a winning formula to close the deal in a major championship," said Spieth, according to Fox Sports.
"The other guys are trying to chase their first. I know how hard it is to chase your first and close it out.
"I need to convince myself by the time I tee off that it's mine and I can go ahead and take some chances because I'm going to have to play aggressive in order to win."
If victorious, Spieth would become the youngest winner of the title since Bobby Jones in 1923.