Conor O'Brien won a State Cup as a Boys-Under-10 player with the Long Island Junior Soccer League's Terryville Fire in 1999.

For those who follow youth soccer in this country, Terryville's national title was a Hollywood–style Cinderella run that would surpass what was seen in either “Miracle” or “Hoosiers.” [2] A Long Island native, O'Brien was one of the most decorated players at Bucknell University, finishing his career 2nd in school history in assists and 9th in goals.

O'Brien found the net 10 times as the club stormed to the 2nd Division West title and then emerged victorious in the promotion[8] Following the 2010–11 season, he signed an eighteen-month contract with SønderjyskE in the Danish SuperLiga.

[11] When struggling to maintain position in the league table, Odense BK seemed to prefer to play a product from the team's youth system rather than the American.

During his stay in Denmark's top flight, O'Brien logged 9 goals and 5 assists across all competitions for Odense BK, SönderjyskE and FC Nordsjælland, for whom he made his Champions League debut in 2013.