"He's a great champion, someone I have lots of respect for and we're going to have a good match, I'm sure."
Federer crushed sixth-seeded Czech Tomas Berdych 7-6 (7-4) 6-2 6-4 in his quarter-final earlier on Tuesday to progress to the last four at a major for a mind-boggling 40th time.
Intent on avenging his shock semi-final loss to Nishikori at the 2014 US Open, Djokovic registered the only break of the first set in the sixth game, then repeated the dose in the first game of the second to have his opponent rattled.
But the Serb wasn't at the top of his own game either.
Coming off a scratchy performance in the fourth round where he hit 100 unforced errors in his five-set win against Gilles Simon, Djokovic struggled to find his rhythm on serve.
He had to save five break points in the second but was able to break again to seal the set.
Nishikori received treatment for a thigh issue twice in the third set but he also enjoyed his brightest period of the match.
Twice he broke the Djokovic serve but each time the world No.1 was able to break back before registering a decisive third.
The Asian superstar has now played in three quarter-finals at the Australian Open without winning a set.
Third seed Federer dismissed Berdych in emphatic fashion and will be playing for a place in the title match in Melbourne for the first time since claiming a fourth trophy in 2010.
"I'm very, very happy. Tomas has caused me a lot of problems over the years," Federer said after making the semi-finals for the 12th time in 13 years.
"He's one of the guys who makes you a better player. He's beaten me around the world on the biggest courts.
"I played a great match."
- AAP
