Since making his World Cup debut in December 2001, Sullivan has one victory, a downhill at Chamonix, France, on January 26, 2008. He won the renowned Kandahar downhill in Chamonix in 2:00.11, ahead of Swiss star Didier Cuche.
In early December 2003, Sullivan injured his knee in a downhill training run at Beaver Creek. It happened at the last jump of the Birds of Prey course and caused him to miss the rest of the 2004 season. While training in France in October 2004, Sullivan reinjured the knee and was out for the 2005 season as well.
In late December 2010, Sullivan crashed during a training run on the Stelvio course at Bormio, Italy (video). He sustained a concussion which ended his 2011 season, including the 2011 World Championships. After two months, he was cleared by doctors to get back on skis in early March.