WASHINGTON -- Nationals third baseman Ryan Zimmerman, outfielder Josh Willingham and pitchers Shawn Hill and Scott Olsen formally filed for arbitration on Thursday.

The Nationals are expected to exchange salary figures with the four players on Tuesday.

Arbitration hearings are held from Feb. 1-21, but the two sides can still reach an agreement up until the scheduled meeting. Nats general manager Jim Bowden declined to comment on the arbitration process.

Of the four players, Zimmerman is the biggest name. Zimmerman and the Nationals have been trying to work out a multiyear deal since last Spring Training.

During that period, Washington vowed not to spend excessively, but the club was willing to give Zimmerman a contract that was similar to that of Rockies shortstop Troy Tulowitzki, who signed a six-year, $31 million deal in January 2008. Sources indicated then that Zimmerman wanted a larger contract.

Zimmerman's contract was renewed, and he made $465,000 in 2008.