Although a Red Sox official with direct knowledge of the negotiations told ESPNBoston.com's Gordon Edes on Tuesday that "it's likely he's going to go but nothing has been finalized,'' WEEI radio in Boston reported on Wednesday that a deal had been reached.
Epstein would receive a five-year contract for in excess of $15 million from the Cubs, but a title had not been agreed upon, according to the report.
The Red Sox and Cubs were still negotiating compensation that Boston would receive from Chicago for Epstein, who had one more year left on his Red Sox contract. An industry source told Edes Wednesday that the deal was "not done," and WEEI reported that talks could continue until the end of the week.
The Cubs' negotiations with Epstein about taking over the top baseball job in the organization have been going so smoothly that the team has asked Major League Baseball what protocol will be for compensation if Epstein decides to join the Cubs, a source with knowledge of the negotiations told ESPNChicago.com's Bruce Levine.
A source with knowledge of the talks told ESPN's Karl Ravech that the compensation would involve prospects and/or cash, but no major league players would be part of the deal, following traditional precedent.
Also, Epstein's title with the Cubs would be above his current title of executive vice president/general manager of the Red Sox, a source told Levine.
"Nothing will be resolved as quickly as has been speculated,'' a source close to the negotiations told Edes, "and it is still unclear how this will be resolved.''
The Boston Herald first reported that Epstein was on the cusp of joining the Cubs.
Since the possibility of Epstein going to the Cubs first surfaced in August, Red Sox ownership has downplayed the possibility because Epstein is under contract with the Red Sox through 2012. But at no point have Red Sox owners John Henry or Tom Werner ever squashed the talk completely, nor has Epstein definitively ruled out the move.
Neither the Cubs nor Red Sox have formally acknowledged that the Red Sox granted permission to the Cubs to interview Epstein, but an industry source said Tuesday that Cubs owner Tom Ricketts spoke with Epstein last week and that Epstein met with Cubs president Crane Kenney in Chicago last weekend.
Sources indicated last week that the Red Sox have had informal conversations about changes in the event that Epstein did leave for the Cubs -- and at the top of their hierarchy, there have been some discussions about the identity of the next manager without Epstein.
The Red Sox also have had informal conversations about candidates other than assistant GM Ben Cherington to replace Epstein, were he to leave. But Cherington appears to be the heir apparent if Epstein departs.
If Epstein leaves the Red Sox, he will likely be restricted, in an agreement between the teams, from bringing any Boston employees with him without approval from the Red Sox, according to an American League source.
Executives with the Red Sox either declined comment or did not respond to requests for a response. Epstein did not respond to a request for comment, although there were indications Tuesday night that the Red Sox were hoping that Epstein might yet change his mind.
But one Red Sox official said Tuesday that Epstein's departure would not come as a surprise.
"It wouldn't shock me,'' the official said, "but until it happens I won't believe it.''
The last two Red Sox forays into hiring a general manager have taken last-second twists. In 2002, the Red Sox struck an agreement with Oakland's Billy Beane to become GM, only to have Beane call Henry two days later to inform him that he had changed his mind. That opened the way to Epstein's hiring.
Then in 2005, Epstein left the club in a dispute with CEO Larry Lucchino, and the team subsequently hired Cherington and Jed Hoyer as co-general managers. Epstein's departure was short-lived; he was back as GM within three months, with Hoyer later leaving to become general manager of the San Diego Padres.
Cherington's first order of business, if promoted, would be to hire a manager to replace Terry Francona, who left after eight seasons in the job. In Chicago, Epstein would be replacing Jim Hendry, who was let go in July after becoming Cubs GM in 2002, the same year Epstein began with the Red Sox.
The Cubs have a manager under contract for one more year, Mike Quade.
ESPNBoston.com's Gordon Edes contributed to this report.