The former Kansas Jayhawk became the primary pivot for the Chargers in 1964, and he proceeded to be an AFL All-Star that season, and in 1965, where he led the AFL in Passing Yards (2,798). Hadl eclipsed that mark in 1966 (2,846), did better again in 1967 (3,365) and was again first in 1968 (3,473), and for the first time, he was first in Touchdown Passes (27), though he also topped the leaderboard in Interceptions (31).
Hadl had another strong season in 1971, where he once again led the league in Passing Yards (3,075) and Passing Touchdowns (21), and in 1972, his last year with the Chargers, he was a Pro Bowler.
Hadl was traded to the Los Angeles Rams after that year, and as a Charger, he threw for 26,938 Yards and 201 Touchdowns against 211 Interceptions. In 1983, Hadl was inducted into the Chargers Hall of Fame.