McCarthy graduated from Camden Catholic High School in 1935 and Saint Francis University in 1942, where he was named to the first-team of the Little College All-American Football Team for 1941.
McCarthy played for "Card-Pitt", a team that was the result of a temporary merger between the Chicago Cardinals and the Pittsburgh Steelers.
The teams' merger was a result of the manning shortages experienced league-wide due to World War II.
During a game against the Green Bay Packers, McCarthy's 35 yard-per-punt average emboldened Card-Pitt to release Johnny Martin.
At the end of the season, the Card-Pitt passers completed just 31% of their attempts, with eight touchdowns and 41 interceptions (a record at the time, and still the third highest total in NFL history).