Don Mattrick, the man in charge of the Xbox division at Microsoft, is leaving to become CEO of Zynga. 

Confirming the appointment in an email, Microsoft CEO Steve Ballmer told employees: "Zynga announced today that Don Mattrick would be its new CEO, effective July 8. This is a great opportunity for Don, and I wish him success.

"Don’s directs will report to me and will continue to drive the day-to-day business as a team, particularly focused on shipping Xbox One this holiday."

The move, which must have been in the planning for some time, will see Microsoft without a lead for its new console in the run-up to the global launch of the console later this year and could cause trouble for Microsoft if a replacement isn't found quickly. 

Mattrick, who has been at Microsoft for some time, has worked within Microsoft's interactive entertainment business for over six years. 

"Since joining IEB more than six years ago, Don and his team have accomplished much. Xbox Live members grew from 6 million to 48 million. Xbox 360 became the No. 1 selling console in North America the past two years,"Ballmer said in his letter to staff. 

"We introduced Kinect and have sold more than 24 million sensors. We released fantastic games, and, most importantly, we expanded Xbox to go beyond great gaming to deliver all the entertainment people want — sports, music, movies, live television and much more," 

Ballmer thanked Mattrick, saying that he was responsible for "setting us on a path to completely redefine the entertainment industry".

A replacement has yet to be confirmed. 

Meanwhile, Mattrick will have his hands full starting next week, taking over from founder/CEO Mark Pincus, and trying to save Zynga from falling profits and a not so rosy outlook.