The news comes two days after Morgan said he didn't fit in with the Nationals, comments that disappointed manager Jim Riggleman.
General manager Mike Rizzo said Morgan's comments to MLB.com had nothing to do with the transaction.
"Players say things out of frustration all the time," Rizzo said. "I had a great meeting with Nyjer. He is comfortable where we are at. He feels good about himself. That did not play into it at all."
Morgan, who was on the trading block for at least a week, was aware the Nationals planned to use Rick Ankiel -- who will platoon with Jerry Hairston Jr. this season -- as their Opening Day center fielder. According to a baseball source, the team made the decision on Ankiel more than a week ago.
"We figured," Rizzo said, "given the state of the roster and the players that we have on it, I thought it was a prudent move to get a young player that we really like and break the logjam in center field.
"It wasn't what Morgan didn't show -- it's what Ankiel did show. Ankiel did show us that he could go get the ball in the outfield. His arm is really a weapon. When he is out there, there are very few players that are going from first to third, second to home. He can create a lot of damage with one swing of the bat. I focused more on what Ankiel did, not what Nyjer didn't do."
2010 Spring Training - null
Sights & Sounds
Spring Training Info
Morgan had been Washington's primary leadoff hitter for more than a year, and he is coming off a season in which he hit .253 with 24 RBIs and 34 stolen bases. The Nats were hoping Morgan would play winter ball in the Dominican Republic, but he declined, wanting to get over a season in which he was involved in a benches-clearing incident with the Marlins.
Morgan entered Spring Training as the incumbent in center field, but had to improve his offense against left-handed pitching, have a high on-base percentage and play quality defense to keep his job. Entering Sunday, Morgan was 13-for-54 (.241) with a home run and five RBIs, and there are those within the Nationals' organization who believed Morgan had been subpar defensively in center.
"He was completely professional. He understood [the trade might happened]," Riggleman said. "He was battling for a center-field job. I think he probably figured that something might happen.
"In talking to him, Nyjer was grateful for the opportunities he got here. He is looking forward to helping Milwaukee."
With Morgan no longer in the mix, Riggleman announced that shortstop Ian Desmond will be the leadoff hitter. Last season, Desmond had a .308 on-base percentage, while batting mostly second and eighth. The last time Desmond hit at the top spot on a consistent basis was while playing in 'A' ball.
Desmond is confident he could do the job as the team's leadoff hitter.
"I'm going to go up there and do what I can," Desmond said. "I worked hard in Spring Training as far as pitch recognition, trying to put the ball in play and trying to be a little more productive on the basepaths. I'm looking forward to the challenge."
Dykstra, who will turn 22 in June, was one of Milwaukee's second-round picks during the 2008 First-Year Player Draft. He tumbled down the list of top Brewers' prospects during a tough '09 season during which he batted .234 for a pair of affiliates and switched from center field to the infield. He mostly appeared at third base last season at Class A Wisconsin and rebounded at the plate, batting .312 with a .416 on-base percentage in 100 games.
His father is former big league All-Star Lenny Dykstra.
Rizzo's philosophy is to be more athletic, and that's why the Nationals acquired Cutter Dykstra. The team has not decided which affiliate he will play for in the Minor Leagues, but Dykstra is expected to report to Minor League camp on Monday.
"He is an athletic kid and he is a really good runner," Rizzo said. "He has really good speed. He is a good offensive player, a high on-base-percentage guy. He works counts. He is the type of guy that could hit at the top of the lineup. He has a little pop and really commands the strike zone."
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the time He also could be found on Twitter @WashingNats. MLB.com reporter Adam McCalvy contributed to this report. This story was not subject to the approval of Major League Baseball or its clubs.