"We have been committed to providing Elijah the support needed to get his personal and professional life back on track," said senior vice president of baseball operations Andrew Friedman. "He has made progress, and a logical next step is a change of cities and a fresh start for him and his family."
Before being finalized on Monday, Friedman said discussions with the Nationals dated back four to six months.
"The idea and the spirit behind everything we were doing was to put Elijah in the best possible position to succeed on and off the field," Friedman said.
Gibson, 20, was the Nationals' fourth-round pick in the 2006 First-Year Player Draft out of Center Moriches (N.Y.) High School in Long Island. Last season, Gibson pitched for Class A Vermont of the New-York Penn League, and he went 4-3 with a 3.10 ERA in 12 starts.
Gibson was recognized by Baseball America this offseason as having the best changeup and best control in the Nationals' farm system. Previously, the publication listed Gibson as having the best curveball in Washington's system. Gibson is the son of former Major League pitcher Paul Gibson, who pitched for the Tigers, Mets and Yankees from 1988-96.
Dukes, 23, has not played for Licey in the Dominican Winter League since Thursday night, when he was ejected from the game. Friedman said the incident had no effect on Monday's trade, since the deal was close to being consummated at that point.
Friedman said he had a "very good conversation" with Dukes after the trade, in which Dukes thanked Friedman and the Rays for their support over the past six months.
"He was very appreciative and seemed to understand the fresh start for him was in his best interest," Friedman said.
Rays manager Joe Maddon called the trade "good for him and good for us at this particular point."
"A large part of it is, for him to be successful -- and it's been discussed often -- is to get him into a different city, a different environment entirely so he can get away from the Tampa Bay area in general," Maddon said. "So that in and of itself can help him. And obviously from our perspective, we want to maintain what we're doing in the clubhouse right now and maintain the chemistry that we saw really grow. ... I think this is good for Elijah, and I think it's good for us. This kid [Gibson], I'm hearing a lot of interesting stuff [about him]."
Dukes said he was excited about getting a fresh start with an "up-and-coming franchise like the Washington Nationals.
"It's an important move for my career and gives me the chance to prove myself both on and off the field. I appreciate this opportunity, and I'm looking forward to meeting the fans of Washington, D.C., as we move into a brand-new ballpark."
After a series of domestic problems, coupled with a history of anger-related issues, Dukes was optioned to the Minor Leagues in June and placed on the temporary inactive list.
Dukes began the year in center field for the Rays, but his season started to go downhill after a May 23 St. Petersburg Times report alleged that he threatened to kill his estranged wife and their kids.
Later in the summer, Dukes called a Tampa Bay radio station to defend himself and his family, while making accusations against his wife. After that episode, Rays officials took a stance that made it clear they felt Dukes had become a distraction and placed him on the temporary inactive list. He did not play for the Rays again during the 2007 season.
Dukes hit .190 with 10 home runs and 21 RBIs in 52 games.
Bill Chastain is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.