Farr was selected by the Detroit Lions in the first round, seventh overall pick, of the 1967 NFL Draft. As a rookie for the Lions in 1967, Farr rushed for 197 yards in a game against the Minnesota Vikings, totaled 1,177 yards from scrimmage, and ranked fifth in the NFL with 860 rushing yards. He led the Lions in both rushing yardage and with 39 receptions, and he was selected by the United Press International as the NFL Rookie of the Year. The Associated Press picked Farr as the Offensive Rookie of the Year and teammate Lem Barney as the Defensive Rookie of the Year.