Retzlaff remained undefeated through his first 23 bouts, losing for the first time by disqualification against Antonio de la Mata in Chicago in November 1930.
Retzlaff scored three knockdowns and a first-round knockout en route to winning the vacant Minnesota State Heavyweight Title.
"[3] At the end of 1935 Retzlaff was ranked by Ring Magazine among the top ten heavyweight boxers in the world.
[4] In January 1936 Retzlaff lost by first-round knockout to a young prospect named Joe Louis.
[3] In his final defense of the Minnesota heavyweight title Retzlaff could manage only a draw against 17-9 Arne Andersson.