Riddoch's resignation accompanies an admission from the SRU's top official that the organisation's marketing and business procedures are in need of a drastic overhaul.
Responding to Riddoch's departure, SRU chief executive Gordon McKie said that a review of the governing body's trading practices had concluded that major changes are needed.
McKie said in the Telegraph: "We have recently reviewed all commercial and marketing activities within Scottish Rugby and have concluded that a new structure is needed. To this end, a new Head of Commercial will be appointed."
The Times reports Dominic McKay, the director of communications, denied this was a significant change of tack, saying it was more of an adjustment to difficult trading conditions. “The role will be to manage all the commercial properties of the SRU, including those of the pro teams,” he said. “It will leave the chief executives of both Glasgow and Edinburgh free to concentrate on things like brand identity and attendances.”
The new appointment will result in all major commercial decisions for both Edinburgh and the Warriors being taken at Murrayfield rather than by the pro-team's chief executives.
The Scotsman claims the removal of the those resonsibilities is to be accompanied with a drop in salary. It appears Riddoch's response was a swift 'no thanks', but Edinburgh CEO Nic Cartwright is believed to have accepted the new deal.
In the Herald Riddoch said: "The Warriors now have a long-term playing venue at Firhill andwill shortly move into their new world-class training facilities at Scotstoun. This will provide the necessary consistency and facilities the club needs to continue its progress and challenge the leading rugby teams in Europe both on and off the field.
"The last two years have been all about building strong community foundations to ensure that the Warriors are ideally placed to flourish in Glasgow. There are strong signs from the schools, grassroots rugby clubs, the media, the business community and the public that the Warriors will continue to go from strength to strength."