Claim: Jackie Fields had never lost in his professional career in boxing, a combat sport in which two people, usually wearing protective gloves, throw punches at each other for a predetermined amount of time in a boxing ring.
Evidence: With only six fights and nine months of professional boxing to his credit, Fields lost badly in a second-round knockout at Olympic Auditorium in Los Angeles. 
Fields piled up a points lead in the early rounds, but Thompson came back with jabs and uppercuts in close fighting that badly wore down the reigning champion. 
Fields lost his NBA welterweight title on February 22, 1933 against Southpaw Young Corbett III before 15,000 fans in a ten round points decision at Seals Stadium in San Francisco.