Washington Nationals third baseman Ryan Zimmerman has signed a six-year contract extension with the Nationals worth $100 million with a club option for the 2020 season. Zimmerman had been due to become a free agent after the 2013 season.

I have mixed feelings about the extension. In the short term it’s a good move. The Nationals are on the cusp of contention and could be a force to be reckoned with over the next four or five seasons. Indeed, they have a legitimate shot at winning the NL Wild Card in 2012. But I see a couple of problems.

First, can Zimmerman stay healthy? He missed two months of the 2011 season with an abdominal strain. Previously, he missed a substantial amount of time in 2008 due to a shoulder injury.

Second, the Nats have closed to $250 million tied up into two players, Zimmerman and Jayson Werth. Prior to last season, Werth signed a seven-year deal worth $126 million. Unfortunately, Werth struggled mightily in 2011 hitting .232 with 20 homeruns and 58 RBI. Even if Werth rebounds in 2012 and Zimmerman is injury free, the Nats have limited flexibility in the long term. If Stephen Strasburg and Bryce Harper turn out to be bonafide superstars it is hard to imagine the Nats being able to keep them on the payroll along with Zimmerman and Werth especially after they become arbitration eligible. The same could be said for the likes of Drew Storen, Ian Desmond and Danny Espinosa.

Nevertheless, Zimmerman has put together a good career, if not an underappreciated third baseman and has been a solid citizen as the face of the Washington Nationals franchise.