According to Ken Rosenthal of FOX Sports, the Washington Nationals are closing in on an agreement with star third baseman Ryan Zimmerman on a contract extension. Zimmerman's contract does not expire until the end of the 2013 season, but he will reportedly test the free agency waters if he enters the 2013 season without a new contract. Negotiations have been ongoing for over a month, and Zimmerman does not want to continue negotiations into spring training, which officially begins Saturday.
However, Rosenthal mentioned that the deal is not done yet and that there are potential "deal-breakers". He elaborated on that and the proposed contract length in another tweet.
Zimmerman's current contract pays him a total of $45 million over five years, and it makes him one of the best paid players on the team. His numbers took a slight dip last season, but he was extremely productive in his 2009 and 2010 seasons, and will command a large contract in free agency if he pulls himself back up to that level and decides to test the waters in 2013.
(Update: One of the remaining hang-ups is reportedly the no-trade language in the contract.)