Mendes was a late entry to the bout, stepping in to replace Jose Aldo after the featherweight champion was forced to withdraw from the fight due to a rib injury.
Despite the short time that he has had to prepare for the fight, Mendes is feeling confident, in part due to McGregor's slim physique.
"He looks scrawny. He's cutting too much weight," he said. "He's skinny. I'm gonna destroy this dude. He's a one-dimensional fighter.
"He's a stand-up fighter. Bottom line. He doesn't have anything else. I'm more well-rounded. I have power. I can put people to sleep on their feet, I can take you down and beat a hole in your face and I can submit you. What else can he do?"
The 30-year-old Mendes heads into the fight with a 17-2 record, with both defeats coming at the hands of Aldo.