The Red Sox will get a low-level prospect after the Rule 5 draft for Doubront, a source told ESPNChicago.com's Jesse Rogers.
Doubront struggled with the Red Sox this year, going 2-4 with a 5.19 ERA in 10 starts before being moved to the bullpen June 24. In seven games as a reliever, Doubront's numbers were even worse -- 11 earned runs surrendered on 15 hits in nine innings pitched.
The majority of that damage came on Monday night -- Doubront's last outing in a Red Sox uniform -- as the 26-year-old allowed six runs on six hits while only recording two outs. To observers Doubront seemed disinterested on the mound, perhaps a result of his reportedly expressed desire to return to the team's starting rotation days earlier.
"I don't know that two nights ago triggered a trade," manager John Farrell said Wednesday. "I don't think any trade just happens overnight."
Showing up to spring training in great shape, hopes were high for Doubront to finally put it all together this season after he showed flashes of excellence at several points in his previous four seasons with Boston. Instead, Doubront struggled out of the gate, including a stint on the disabled list with shoulder fatigue that caused him to miss several starts. Farrell mentioned this, along with a lack of consistency, as possible reasons for why Doubront never pitched to expectations this season.
"I can't say that it was one thing," Farrell said. "But he seemed to never get on a roll like he did last year in those  straight starts [May 16-Aug. 10] of three runs or less. That was missing this year.
"He has performed well for us over a period of time," Farrell said. "And it can't be understated the importance of his relief appearances last year in the World Series [4 2/3 innings with one run between Games 3 and 4]. Those were two pivotal outings by him and he did a great job."
The Cubs will represent a degree of familiarity for Doubront, as Theo Epstein, Chicago's president of baseball operations, was general manager of the Red Sox when the club signed Doubront as an amateur free agent out of Venezuela in 2004.
Overall, Doubront went 26-22 with 4.82 ERA in his five seasons with the Red Sox.