Microsoft has removed Andy Lees as the head of the Windows Phone project, and has shifted his prior responsibilities to Terry Myerson. Myerson was previously the engineering lead for the project.

According to AllThingsD, who broke this story, he will take on the responsibilities of Lees’ former role, but will not take on his title. The Windows Phone project launched over a year ago, but has had struggles to gain market traction.

An internal Microsoft memo reveals the official verbiage on the move, with Ballmer saying that “I have asked Andy Lees to move to a new role working for me on a time-critical opportunity focused on driving maximum impact in 2012 with Windows Phone and Windows 8. We have tremendous potential with Windows Phone and Windows 8, and this move sets us up to really deliver against that potential.”

If this was an effective firing, or simply a change in structure is not known at this time. TNW has a request for comment in with Microsoft and will update this post upon hearing back.

It seems odd that Microsoft has pulled Lees without having a firm replacement at the ready. This could be due to his removal being tumultuous, a conflict perhaps, or simply faith in Myerson to handle the division until something permanent can be arranged. Or, it could be that Myerson simply doesn’t want to run Windows Phone, and is thus merely taking the reins until he can step aside and return to full-time engineering work; in this scenario Microsoft would not name him as the, to prevent it appearing, upon his concession, that it can’t keep the leaders of Windows Phone in place.

This change will likely have little short term impact on the phone line’s commercial potential, so its performance this holiday sales cycle will remain the strong baramoeter that we are expecting it to be.