The magazine did not specify a reason for the departure of 46-year-old Larry Platt, whose departure comes two months before his contract was set to expire.
Platt e-mailed the staff Friday and said a recent meeting with the magazine's owners was "difficult."
After the meeting, he says it became clear to him that his time at the magazine "has run its course."
The magazine's president, David H. Lipson Jr., says Platt's departure "happened kind of fast" and that "not one thing" had been at issue.
Forty-six-year-old Tom McGrath, executive editor since 2005, was named interim editor.
Platt, a longtime sportswriter, says he will return to writing.
