Per a tweet from Yahoo's Jeff Passan:
Source: Atlanta finalizing deal to acquire catcher/outfielder Ryan Doumit from Minnesota.— Jeff Passan (@JeffPassan) December 18, 2013
The news was later confirmed by the Twins, who sent out this news release:
The Minnesota Twins announced that they have traded catcher/outfielder Ryan Doumit to the Atlanta Braves for left-handed pitcher Sean Gilmartin. Doumit played in 269 games for the Twins from 2012-13, hitting .261 (253-for-969) with 62 doubles, 32 home runs and 130 RBI. He is a career .268 hitter (787-for-2936) with 187 doubles, 99 home runs and 396 RBI in nine major league seasons with the Twins and Pittsburgh Pirates.
Gilmartin, 23, went 3-8 with a 5.74 ERA (91.0 IP, 58 ER), 33 walks and 65 strikeouts in 17 starts for Triple-A Gwinnett (International League) last season. He has a career record of 12-20 with a 4.23 ERA (285.1 IP, 134 ER), 74 walks and 223 strikeouts in 54 games (53 starts) during three seasons in Atlanta’s minor league system.
The 6-foot-2, 190-pounder was drafted by the Braves in the first round (28th overall) in the 2011 First-Year Player Draft out of Florida State University. Gilmartin will be signed to a minor league contract and will be invited to Twins Spring Training.