Nurmagomedov, who was promoting his upcoming fight with interim lightweight champion Dustin Poirier, questioned why McGregor merited a second chance at the belt.
"The last three years he has only one victory and amateur boxing. How does he deserve a rematch?" Nurmagomedov asked. "He tapped. He begged me, 'Please don't kill me.' Now he's talking about a rematch?
"Tony Ferguson [is] on the line. People who have win streaks [are] on the line. But not the guy who don't win nothing the last three years. ... Right now I'm focused on Sept. 7."
Nurmagomedov and Poirier will fight for the unified title on that date in the main event of UFC 242 in Abu Dhabi. Poirier (25-5-1) has won four in a row, most recently a unanimous decision victory against featherweight champion Max Holloway -- who had moved up in weight -- at UFC 236 in April.
Nurmagomedov, of Dagestan, has not lost in 27 professional fights. He submitted McGregor at UFC 229 last October by fourth-round neck crank. After the fight, Nurmagomedov jumped out of the Octagon and into the crowd to fight a member of McGregor's team and a brawl ensued. Both fighters were fined and suspended. Nurmagomedov is eligible to return next month.
The winner of Nurmagomedov vs. Poirier is expected to face Ferguson, who is riding a 12-fight win streak. He defeated Donald Cerrone at UFC 238 this past weekend by second-round TKO. Nurmagomedov and Ferguson have been matched up together on multiple occasions, and each time the bout has fallen through.
"He deserves a title shot, in my opinion," Nurmagomedov said. "But when the UFC asked him to fight Max Holloway, he didn't take that fight. Right now, the problem is because of him. I don't know why he didn't take that fight. He took a regular fight with Cowboy [Cerrone]. I don't understand this.
"I don't want to underestimate my opponent, Dustin. He's a tough challenge for me and right now I don't want to think about other opponents."