It is believed the Nats are in competition with the Mariners and Cubs. There were reports that the Rangers were also in the running for Fielder's services, but the source believes Texas will stick with Mitch Moreland at first base.
The source indicated that Nationals ownership will make the final decision on whether the club signs Fielder. It's not known how many years or how much money Washington is willing to give Fielder.
For weeks, Nats general manager Mike Rizzo indicated that Adam LaRoche would be the starting first baseman for the 2012 season.
Last Spring Training, LaRoche was diagnosed with a torn labrum and rotator cuff. He only played in 43 games, hitting .172 with three home runs and 15 RBIs.
During LaRoche's absence, Mike Morse, and later Chris Marrero, emerged at first base. LaRoche said in October that the Nats didn't promise that he would play every day at the position next season. LaRoche is set to make $8 million in 2012 in the second year of a two-year deal. There is a mutual option for '13.
If the Nationals want to trade LaRoche, it most likely would not happen until Spring Training. Opposing teams would want to see if LaRoche has fully recovered from his shoulder injury.
"Obviously, anything can happen. That's their decision," LaRoche said in October. "That's a pretty big investment for someone who is not playing. I don't know what direction they would go. Obviously, anything is possible."
During the Winter Meetings, Washington appeared reluctant to consider Fielder, 27, in fear that he would be no more than a designated hitter in a few years.
If the Nats are able to sign Fielder, they would have significant power in a lineup that includes Morse and Ryan Zimmerman. They would also show the baseball world that they are serious about competing for the National League East title. Washington already acquired left-hander Gio Gonzalez from the A's and now has one of the NL's better rotations, featuring Stephen Strasburg and Jordan Zimmermann.
One baseball source indicated on Sunday to never underestimate the relationship between the Nationals and Boras, who represents Fielder and several members of the Nats, including Strasburg, Jayson Werth and Bryce Harper.
When asked about Fielder being linked to the Nationals, another source said: "I think Boras is using [the Nats] to drive up the price with interested teams."
This season, Fielder hit .299 with 38 home runs and 120 RBIs for the Brewers. During his seven years in Milwaukee, Fielder is a career .282 hitter with 230 home runs and 656 RBIs.
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. This story was not subject to the approval of Major League Baseball or its clubs.