Neumann's mooted departure from Opel comes as the position of a top executive at Neumann's former employer, Volkswagen Group, has been called into question in the wake of a scandal over rigged emissions tests. The embattled chief executive of VW's Audi division, Rupert Stadler, only got a five-year contract extension last month because of an agreement among supervisory board members that he would not serve out his full term, two sources have told Reuters. Opel's Neumann in 2013 joined GM to lead the U.S. carmaker's European operations, which include the Vauxhall brand, after losing out in a management reshuffle at Volkswagen. ($1 = 0.8935 euros) (Editing by Alexander Smith/Hugh Lawson)