Nationals Closing In On Extension With Zimmerman

3:10pm: Chico Harlan of the Washington Post says the Nationals are closing in on a five-year, $45MM extension with Zimmerman.  The deal would begin with 2009, erasing his current contract.  By comparison, Markakis will earn $47MM over the same service time slice of his career.

2:35pm: According to Ken Rosenthal of FOX Sports, the Nationals are closing in on an extension with third baseman Ryan Zimmerman.  The talks are getting serious, with Zimmerman aiming for a deal similar to Nick Markakis' six-year, $66.1MM deal.  Rosenthal says a Zimmerman extension "likely would cover his remaining arbitration years and at least two years of free agency."  Markakis' deal bought out all three arbitration years and three free agent years with a mutual option for a fourth.

Looking at Zimmerman's accomplishments, is he worth a big-money extension?  Or are the Nationals locking him up because he's their best young player?