Eckhard was an accomplished amateur who won 66 of 80 contests. When he was not picked for the 1972 Olympic team in Munich, he decided to turn pro in 1973. He won his first thirteen fights beating the likes of Matt Donovan, Denny Moyer, Manuel Gonzalez and former world champion 
Billy Backus. He lost his first fight in 1974 to future world champion Jose Manuel Duran. Dagge was stopped in round eleven. This was for the European 154 pound title. A year later Dagge halted Duran in a rematch to claim the EBU crown.
Another future world champion, Vito Antuofermo would beat Dagge in 1976 to take the EBU honors. Later that year Dagge became the first German to win a world title since Max Schmeling when he knocked out Elisha Obed to capture the WBC title. Eckhard made two very tough defenses. He won a highly controversial decision over the great former welterweight and middleweight champion Emile Griffith. Next future world titleholder Maurice Hope held him to a draw.
On August 6, 1977 Dagge lost his WBC crown to Rocky Mattioli. Eckhard retired in 1981 after 32 fights. His career record was 26-5-1. He scored 15 knockout victories. After his retirement he became a trainer and once worked with Dariusz Michalczewski.