Tom Mueller, the president and chief operating officer of Wendy’s International, has resigned, effective immediately. Jack Schuessler, chairman and chief executive of Wendy’s International, will assume Mueller’s role on an interim basis. Schuessler said: "We will reinvigorate sales growth with a fanatical approach to execution in the areas of restaurant operations, marketing and R&D." No reason was given for the move, although analysts pointed to the group’s falling sales as a likely cause.