"It's finals of the Grand Slam. I've been in this situation before in 2007, so I'm more experienced than Rafael," said Djokovic.
"But it's gonna be definitely a tough one. Rafael is just playing fantastic tennis. He's gonna be very motivated to win this title because it's the only title he hasn't won in majors."
Nadal is the reigning Wimbledon and French Open champion who has never reached a US Open final. The world number one superstar needs a US Open title to complete the career Golden Slam, which is all four majors and an Olympic gold medal.
Djokovic, whose only Grand Slam title came at the 2008 Australian Open, seeks his 18th career crown. He had lost six of prior eight Grand Slam semifinals, including his past four in a row.