Fellers' riding career began at the age of 11 when he was given a two-year-old Appaloosa for his birthday. The pair quickly grew close with the help of Fellers’ mother and local riding instructors. The short, stocky horse had a talent for jumping, and the pair eventually became winners from the West Coast U.S. Grand Prix circuit to Spruce Meadows in Canada. In 1991, Fellers was a member of his first U.S. team at the Pan American Games in Havana, Cuba, and his global success has spanned decades. The turning point of his career will be the meeting with Flexible, his life horse. The Irish stallion has offered Fellers the best wins he could ever dream about. In second position at the World Cup Final of Goteborg in 2008, they have won the 2012 one in 's-Hertogenbosch. The same year, part of the USA's team at the London Olympics, they will finish 8th of the individual competition. In 2015, Fellers and Flexible competed in the World Cup Final once again in Las Vegas, finishing seventh. Now aged of 20, Flexible is still on the top of his shape, for exemple, he was in 3rd position of the Spruce Meadows Grand Prix in June.