DALLAS -- The Nationals have made an offer to free-agent left-hander Mark Buehrle, a team source confirmed to MLB.com on Sunday night. Terms of the offer were not disclosed.

The Nationals have made it clear that Buehrle is their top target. A couple of weeks ago, general manager Mike Rizzo said he wanted a veteran starter who could help a young rotation that includes Stephen Strasburg and Jordan Zimmermann.

Buehrle has thrown 201 or more innings for 11 years in a row and has also been regarded as a good guy in the clubhouse.

This past season, Buehrle was 13-9 with a 3.59 ERA in 205 1/3 innings for the White Sox.

If the Nats are unable to sign Buehrle, look for the club to try hard to sign Roy Oswalt, who has pitched over 200 innings in a season eight times. This past season, Oswalt, 34, pitched in a career-low 23 games for Philadelphia, going 9-10 with a 3.69 ERA. He missed over a month because of back issues. The Phillies declined Oswalt's option, making him a free agent, and the Nationals feel he is still healthy enough to make an impact in the rotation.

During his 11-year career, Oswalt is 159-93 with a 3.21 ERA. He has won 20 games in a season twice.

As far as C.J. Wilson is concerned, a team source for the Nationals indicated that the left-hander is not a top target. The source went so far as to say the Nats are unwilling to give Wilson a huge deal.

Rizzo, who is already at the Winter Meetings which begin on Monday, was not available for comment.

Prince apparently not in the Nationals' plans

DALLAS -- A team source told MLB.com that first baseman Prince Fielder is not a target for the Nationals. The source pointed out that the club has Adam LaRoche and Michael Morse at first base.

LaRoche missed most of last season due to a shoulder injury and is expected to be 100 percent by Spring Training.

Morse, the Nationals' MVP, played most of the season at first base, but was switched to the outfield late in the season after the club called up Chris Marrero, who isn't expected to start Spring Training on time because of a torn left hamstring.

Nix agrees to contract terms with Phillies

DALLAS -- A baseball source confirmed that former Nationals outfielder/first baseman Laynce Nix agreed to terms on a two-year deal with the Phillies.

The source said the Nats also offered a two-year deal to Nix.

"I guess he thought he was a better match with the Phillies," the source said.

This past season, Nix was productive during the first half, but injuries forced him to miss a lot of time after the All-Star break. In 124 games, Nix hit .250 with 16 home runs and 44 RBIs.