Rigged (2008) on Netflix

Plot summary

Michael Dublin lives by scams on the underground boxing circuit, drifting from one town to the next and collecting enemies along the way. One night at an illegal car race, a driver whose car he tampered with beats him, and Katherine Parker, a neighbor, gets him out of the trouble by dropping a much heavier man. Impressed, Dublin tracks her down the next morning and asks to act as her promoter. She says no, but when she lands in jail for attending an illegal boxing event, he arranges her release and talks her into a tour. The pair pick up fights in basement bars, warehouses and county fairs, and Parker's name grows. She wants a place as a challenger at a yearly underground boxing event in Miami.