As the Nationals talk to free-agent first baseman Prince Fielder, they face a significant contractual decision on one of their own players – third baseman Ryan Zimmerman.

Zimmerman has informed the team of the exact terms he would accept long-term, according to one major-league source. He has said in the past that he does not want to sign an extension that would restrict the club from making other moves.

Contract negotiations are fluid, but two other sources suggest that an agreement between Zimmerman and the Nationals is within reach. Zimmerman, 27, is under contract for $12 million in 2012 and $14 million in 2013. After that, he is eligible for free agency.

The Nationals could sign Zimmerman to an extension beyond ’13 or award him an entirely new contract – say, a six-year deal that would include new salaries for ’12 and ’13, and keep Zimmerman in Washington through ’17.

A straight six-year extension, on the other hand, would put Zimmerman under contract through 2019. A deal of that length could be too great a risk for the Nationals, considering that Zimmerman has missed significant time with injuries in two of the past four seasons.

Only three players are under contract through ’19 or beyond - Rockies shortstop Troy Tulowitzki and Brewers left fielder Ryan Braun, both of whom are signed through ’20, and Angels first baseman Albert Pujols, who is signed through ‘21.

-Ken Rosenthal