Neusel turned professional in 1930, racking up a 32–0–2 record before experiencing his first lost against Belgian pugilist Pierre Charles via points decision. During this period, Neusel scored wins over top European heavyweight contenders Gipsy Daniels and Larry Gains. In 1933, Neusel followed his contemporary Max Schmeling to America, where he became popular due to his aggressive style. In 1934, he defeated King Levinsky and the futureHall of FamerTommy Loughran. These accomplishments earned him a ranking as one of the Ring Magazine's Top 10 heavyweights, setting up a bout with Schmeling for European supremacy.
First bout with Schmeling
On August 26, 1934 in Hamburg came a very important match for European boxing, Neusel against Schmeling. The venue was the dirt track facility in the immediate vicinity of Hagenbeck Zoo, which boxing promoter Walter Rothenburg had rebuilt within a few weeks in a rushed manner. Though the audience figures vary from 90,000–102,000 it was unquestionably the largest number of spectators in German history. Neusel lost the match via ninth round technical knockout, putting up a valiant effort but ultimately being outclassed by Schmeling.
European contender
After the Schmeling fight, Neusel held another future Hall of Famer in Len Harvey to a 12 round draw. Following up with back-to-back victories over Welsh contender Jack Petersen. In 1935, Neusel returned to America to face former Heavyweight World Title holder Primo Carnera; losing the bout via fourth round knockout. He then returned to Europe and beat South African challenger Ben Foord twice, with both wins sandwiched around a loss to Tommy Farr.
In 1940, Neusel won the German Heavyweight title against Arno Kölblin in Berlin. He lost the title to Heinz Lazek in the latter part of 1940, but regained it against Adolf Heuser in 1942. He lost it for the last time against Hein ten Hoff in 1946. In 1948, Neusel had a rematch with arch-rival Schmeling, 14 years after the initial encounter. This time Neusel prevailed with a points decision victory over 12 rounds. Neusel retired after a knockout loss to in 1950.
