Bratkowski began his playing career at Schlarman High School. He was twice the SEC passing leader under Georgia coach Wally Butts. During his three-year career with the Bulldogs, he completed 360 passes for 4,863 yards. Bratkowski was considered one of college football's greatest quarterbacks of his day and was the NCAA's all-time leading passer until 1961. Today, Bratkowski still ranks sixth on Georgia's list of career passing leaders. He also led the NCAA in punting his senior year with a 42.6 yard average.
He was drafted by the Chicago Bears and played five seasons in Chicago. He played for the Los Angeles Rams for three years before being signed by Vince Lombardi for the $100 waiver fee to become the "super sub" to Bart Starr. In Green Bay, he was nicknamed "Uncle Zekie." He became an ideal backup and spot starter during the Lombardi championship era. In a 15-year NFL career, Bratkowski passed for 10,345 yards and 65 touchdowns.
In the 1965 Western Division championship game versus the Baltimore Colts, Bratkowski relieved the injured Bart Starr and led the Packers to a 13-10 victory. The Packers went on to win the 1965 NFL Championship against the Cleveland Browns, in a game played on January 2, 1966.
A superbly conditioned athlete, Bratkowski was an early advocate of aerobic training for pro football players. After his playing career, he served two stints as Packer assistant coach, from 1969-’70 and from 1975-’81. He also coached the Browns, Rams, Jets and Eagles, retiring in 1996.
After his playing career, Bratkowski became quarterback coach/offensive coordinator for Chicago, Baltimore, Indianapolis, Philadelphia and with the New York Jets. He was also a quarterbacks coach with Cleveland and the Jets and worked two stints as a Packers assistant as well as the Baltimore Ravens.
While Bratkowski was coaching the Chicago Bears quarterbacks during the 1973 season, head coach Abe Gibron abruptly promoted him to offensive coordinator. Gibron shortly after pressed him into service for one game as a backup quarterback.