The world number one revealed that his game plan is to be "aggressive" and prevent the Spaniard from settling into the match.
"I need to be aggressive on the court, that's for sure," ESPN quotes him as saying. "I need to step in and try to be in control of the match, otherwise he makes his own rhythm, he makes his own pace on the court. That's where he's very dangerous.
"He's a great competitor. He's somebody that has a lot of respect from all the players because he's playing so many tournaments and works very, very hard.
"You can see because he's basically in his 30s one of the fittest players around and is playing the best tennis of his life in the last 15 months. It's the semis of a grand slam, so I expect a tough match."
Two-time defending champion Djokovic is hoping to secure a sixth grand slam title in Melbourne.