Roy Nelson vs. Antonio Silva set
Nelson, who has lost three of his past four fights, recently raised the possibility of dropping to light heavyweight.
UFC president Dana White has been critical of Nelson's weight, which at times appears to hinder his performance inside the cage.
"I think (Nelson) going to 205 pounds is a great idea," White said Tuesday. "I've been very vocal publicly and behind closed doors to him about taking his career serious."
But any plans Nelson has of moving to light heavyweight will be placed on hold until after he meets Silva at MGM Grand Garden Arena in Las Vegas.
Nelson, the former IFL heavyweight champion, has a professional record of 16-7.
Silva (16-3) will look to rebound from a first-round knockout to Daniel Cormier on Sept. 10. That loss snapped Silva's win streak at three.
The 32-year-old Silva will be making his UFC debut.
In the UFC 146 main event, heavyweight champion Junior dos Santos takes on No. 1 contender Ailstair Overeem.
Dos Santos will be making his first defense of the belt he won Nov. 12 with an opening-round KO of Cain Velasquez.
Overeem, the former Strikeforce titleholder, makes his second appearance inside the Octagon. He earned a title shot against dos Santos on Dec. 30 when he registered a first-round TKO of former UFC champion Brock Lesnar.