First, Bruce Jaffe, the corporate vice president responsible for Microsoft’s acquisitions, announces plans to leave the company at the end of February. Then Charles Fitzgerald, Microsoft’s general manager of Platform Strategy, resigns to join a start-up. And now, Jeff Raikes, the Godfather of Office, says he will retire as Microsoft Business Division president in September after 27 years with the company.

All three departures are blows to Microsoft, but Raikes’s undoubtedly weighs heaviest on the company. “While the cemeteries are full of folks who couldn’t be replaced, this is a big hole for Microsoft,” said JupiterResearch analyst Michael Gartenberg. “This will leave a big gap in the orb …”

It certainly will. Raikes has probably done more to shape Microsoft than just about any other employee, save Gates and CEO Steve Ballmer. He was instrumental in the creation of Microsoft Office, so much so that a 1997 email he wrote describing the strategy behind it was used as evidence against Microsoft in its landmark antitrust case. As Ballmer said in a note announcing Raikes’s departure, “Very few people have contributed more to Microsoft than Jeff.“

Raikes will be replaced by Juniper Networks’ Chief Operating Officer Stephen Elop.