The event, which has not been officially announced by the promotion, reportedly takes place Aug. 14 at the Bradley Center in Milwaukee, Wisc. The main card will air live on the Versus network.
At one time Ludwig was considered one of the top kickboxers in MMA thanks to his 2002 K-1 MAX USA title. He recently snapped a two-fight skid with a split-decision win over Nick Osipczak at UFC 122.
O’Brien probably needs a win to avoid being released by the UFC. He dropped his promotional debut to Paul Kelly at UFC 123. Since the WEC-UFC merger several UFC lightweights have been cut including Kelly.