UFC officials made the announcement on Wednesday.
After a rough 2012 that saw Silva (16-3, 2 NC) lose to Alexander Gustafsson and have a submission win over Stanislov Nedkov overtuned after testing positive for marijuana, Silva has put together back-to-back wins.
He knocked out Rafael Cavalcante in June and soundly defeated Matt Hamill in his last outing on Oct. 9.
St. Pruex (11-5) is riding a three-fight winning streak, knocking out Cody Donovan in his last fight on Aug. 17. The 30-year-old has only lost once since 2010 and has an 11-1 record in his last twelve outings.
UFC Fight Night 35 takes place at The Arena at Gwinnett Center in Duluth, Ga., on Jan. 15. The event is headlined by a middleweight match-up between former Strikeforce champion Luke Rockhold and Constantinos “Costa” Philippou.