In 2008 Villanueva made his global indoor debut at the 2008 IAAF World Indoor Championships and also ran at the Olympics for the first time, competing in the heats of the 800 m at the 2008 Beijing Games. He was the 800 m silver medallist at the 2008 Central American and Caribbean Championships, finishing behind Cuba's Andy González. At the World Military Track and Field Championships in June 2009, he came fourth in the 1500 m. Villanueva won a consecutive 1500 m bronze at the 2009 South American Championships in Athletics, but was the gold medallist in the event at the 2009 CAC Championships. He was selected to run the 800 m at the 2009 World Championships in Athletics (although he had focused on the longer distance regionally) and was eliminated in the first round.