Born in Louisville, Kentucky, Farrell moved with his family to Peru at the age of five and played in the Esther Grande youth team.

After playing three seasons with the Cardinals, Farrell signed a Generation Adidas contract with Major League Soccer and was selected with the first overall pick in the 2013 MLS SuperDraft by the New England Revolution.

Farrell was born in Louisville, but was raised in Peru from ages of five to fifteen, where his adoptive parents were Presbyterian missionaries.

He played there for the Esther Grande de Bentín (EGB) Academy and attended Colegio Franklin Delano Roosevelt, The American School of Lima.

He was named to the NCAA Division I First-Team All-America and won the Big East Defensive Player of the Year Award after the Cardinals only allowed an average of 0.62 goals per game.

Farrell also spent the 2012 season in the USL Premier Development League with the Bradenton Academics and the River City Rovers.

[10][11][12] On March 9, 2013, Farrell made his professional debut in the Revs 1–0 away victory over the Chicago Fire in the club's first game of the 2013 season.