Bergey was born in South Dayton, New York in 1945 and graduated from Arkansas State University in 1969 with a Bachelor of Science degree in Physical Education. He was an All-American with the Arkansas State Indians and has been voted by fans the Top Player in Arkansas State history. He was a charter member of Delta Eta chapter of Kappa Alpha Order at ASU. Bergey set ASU records for best tackling average in a season, most fumble recoveries in a season, most tackles in a game, most tackles in a season, and most career tackles. In 1968, Bergey averaged 19.6 tackles per game. He played in three post-season all-star games during his ASU career; he was selected to the All-Southland Conference team three times and to the Southland Conference All-First Decade Team. Bergey's jersey number 66 was retired by ASU.
Professional career
Cincinnati Bengals
Bergey was drafted by the American Football League's Cincinnati Bengals in the second round of the 1969 Common Draft and was an AFL All-Star in his first year. Bergey started for the Bengals for five years.
Bergey signed a "futures contract" with the World Football League's Florida Blazers that would have taken effect in 1976, after his contract with the Bengals expired. Rather than play Bergey for two lame duck seasons, Bengals coach Paul Brown traded him to the Philadelphia Eagles in exchange for two first-round and one second-round draft picks. The Blazers would not survive beyond the 1974 season, and the WFL itself failed partway through 1975; as a result, Bergey never played a down in the WFL and the futures contract never took effect.
Philadelphia Eagles
Bergey played a key role in the Eagles' subsequent rise, culminating in the trip to Super Bowl XV. With the Eagles, Bergey, a four-time All-Pro, set the NFL record for most interceptions by a linebacker and became the highest-paid defensive player in the league with a four-year contract for $1 million. He earned Eagles MVP status three times. Bergey recorded 233 tackles in a single season with the Eagles. He was a popular player who was the foundation of the "Gang Green" defense that brought the Eagles back to the playoffs in 1978, 1979, and to the Super Bowl in 1980. Bergey had conflicts with guard Conrad Dobler of the Eagles' NFC East rival St. Louis Cardinals, who once spit on him while he was downed and injured. His and Dobler's volitale relationship was ranked by NFL Films at #9 on the NFL Top 10 list of feuds. He retired from professional football in 1981. He was inducted into the Eagles Roll of Honor in 1988. In 2012, the Professional Football Researchers Association named Bergey to the PFRA Hall of Very Good Class of 2012.