Shane Atchison, CEO of digital agency Possible, will take on an additional role as WPP's global client leader for Seattle-based tech giant Microsoft, according to an internal memo obtained by Ad Age.

Replacing Y&R Chief David Sable as the account lead, Mr. Atchison will oversee a holding-company relationship that currently spans 40 countries and a number of WPP agencies, including Wunderman, Y&R, JWT, Burson-Marsteller, Cohn & Wolfe, and Possible, among others.

Mr. Sable will "become a senior advisor to Microsoft and support Shane in this role," the memo stated. Mr. Atchison will also continue to serve as CEO of Possible.

"He has built a stellar reputation for delivering engaging digital experiences for Possible's clients, including Microsoft, AT&T, Disney, Warner Bros. and Boeing," added the company in the memo.

Mr. Atchison, based at Possible headquarters in Seattle, has worked with Microsoft for 20 years.

WPP declined to comment.

Microsoft last April moved the bulk of its multibillion-dollar ad and media business to Interpublic and Dentsu Aegis firms, indicating a fresh-start approach under newly appointed CMO Chris Capossela. Still, WPP held onto a portion of its business. Within the holding company, Wunderman had deep ties with Microsoft and more than a decade under its belt supporting various marketing tasks across brands like Microsoft, Xbox, Bing and Windows, as well as campaign execution in local markets around the globe. Prior to the pitch last year, Y&R also took on creative and digital work, and Possible had won web design work for Surface.

Mr. Atchison is not the only WPP digital executive to take on a role previously handled by a long-time ad exec. Mark Read, CEO of WPP Digital, recently assumed the Wunderman CEO position, replacing longtime CEO Daniel Morel. Wunderman is a CRM and digital marketing agency within the Y&R network.