Red Sox GM Theo Epstein agreed to a five-year, $15 million contract with the Chicago Cubs, according to a report.

Since the end of the Red Sox's season, which ended in the worst regular season collapse of all time, Epstein has been rumored to be headed to the Cubs as the team's next general manager.

Boston's WEEI sports radio station reports that Epstein has agreed to the deal, but that the Cubs haven't decided on an official title for him. The title is expected to be above his current title of executive vice president/general manager of the Red Sox.

The Red Sox granted the Cubs permission last week to speak with Epstein and the deal is expected to be official by the end of the week. The Cubs will likely have to compensate the Red Sox for hiring Epstein, but it'll likely be cash considerations or a minor league prospect - no one from the major league roster.

Epstein would be the second major Red Sox management employee to leave the team this off-season. The team already refused to pick up manager Terry Francona's two-year option and now stand to lose Epstein to the Cubs.

The pair helped guide the Red Sox to their first World Series title in 86 years when the team finally triumphed in 2004 and again in 2007.

But the team spoiled on the stretch of this season after most baseball experts tabbed the team as a World Series favorite. Quite a few of Epstein's free agent signings completely bombed this season -- notably Carl Crawford and John Lackey -- while the team lacked any real chemistry, according to a recent Boston Globe article.

The Globe piece detailed how players, including Lackey, would drink beer, eat fried chicken, and sit in the locker room during games. The lack of structure could have influenced Red Sox ownership to let go Francona and not try to stop Epstein from heading to the Cubs.

Epstein's replacement is likely assistant general manager Ben Cherington, according to ESPNBoston. Cherington served as co-general manager with Jed Hoyer in 2005 when Epstein went on a brief sabbatical after a disagreement with COO Larry Lucchino. Cherington returned to his role as assistant GM when Epstein returned three months later.