WASHINGTON -- Nationals catcher Paul Lo Duca suffered a left knee injury this week while working out in a New York gym.

Lo Duca saw Dr. Andrew Pearle, the Mets' associate team physician, on Friday and had an MRI in New York. Lo Duca will return to Washington on Monday to be looked at by Dr. Ben Shaffer, the Nationals' physician and orthopedist. According to a baseball source, the injury was described as a "tweak."

It has not been determined if Lo Duca will miss time in Spring Training. The Nationals will give an update on Lo Duca's condition next week.

Lo Duca and general manager Jim Bowden were not available for comment and Andrew Mongelluzzi, Lo Duca's agent, is on vacation.

Lo Duca, 35, signed a one-year, $5 million deal plus incentives with the Nationals on Dec. 11.

Escobar on board: The Nationals have signed outfielder Alex Escobar to a non-guaranteed Minor League contract. Escobar is expected to be in big league camp and compete for a spot in the outfield.

This will be Escobar's fourth year in the organization. No one has ever questioned Escobar's talents as a big leaguer, but he has had a tough time staying on the field because of shoulder, foot and ankle injuries. In his three years with the Nationals, Escobar has played in only 33 games -- all in 2006. In those games, Escobar hit .356 (31-for-87) with four home runs and 18 RBIs. He missed the entire 2007 season because of shoulder and ankle injuries.

Escobar is expected to be at the team's fan fest in Viera Fla., on Saturday.

More signings: The Nationals have agreed to terms on 2008 contracts with pitchers Jason Bergmann, Matt Chico, Tyler Clippard, Shawn Hill, Joel Hanrahan, Enrique Gonzalez and Saul Rivera, outfielders Roger Bernadina, Elijah Dukes, Garrett Guzman and Justin Maxwell and catcher Jesus Flores. All 12 players will be in big league camp.

Front-office moves: The Washington Nationals promoted John Dever to senior director of baseball media relations and named Mike Gazda director of baseball media relations.

Dever has been with the Nationals/Expos since 2003, and Gazda joins the Nationals after serving the previous three seasons with the Marlins as media relations manager.