Ferrer has found it difficult to beat Djokovic during previous encounters but the Serbian believes that his opponent is currently playing some of the best tennis that he has ever produced.
"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," said world number one Djokovic.
"You can see because basically he is one of the fittest players around and is playing the best tennis of his life in the past 15 months. It's the semis of a Grand Slam, so I expect a tough match."