If Williams makes the 25-man roster out of Spring Training, he will get a one-year, $500,000 contract with no incentives. If he starts in the season in the Minor Leagues, Williams will earn $15,000 per month.
Williams will be one of 11 pitchers who will compete for four spots in the starting rotation. Right now, John Patterson is the only pitcher in the organization with a guaranteed spot in the rotation.
Williams, 25, once was considered a top prospect in the Giants organization, but shoulder and elbow injuries hampered him in 2004 before he was traded to the Cubs during the 2005 season.
Williams spent last season in the Cubs and Athletics organizations. He appeared in five Major League games in '06 and gave up 10 runs in 12 1/3 innings. Williams is 23-24 with a 4.03 ERA in 70 games (65 starts) spanning portions of four big-league seasons.
"He is only 25 years old. He has had some success in the big leagues," general manager Jim Bowden said. "We are trying to find as much pitching as we can. If we can get them back to what their potential is, instead of having it one year, they could be long-term."
Claussen, 27, received a Minor League contract. He will be in the Nationals' big-league camp while continuing to rehab from left shoulder surgery, which took place on Aug. 14.
Claussen is 16-27 with a 5.04 ERA in 58 big-league starts spanning four seasons with the Reds and Yankees. His best season came in 2005, when he went 10-11 with a 4.21 ERA in 29 starts for the Reds.
"He is a left-handed pitcher that won in double digits and had a four ERA in a bandbox [Great American Ball Park]," Bowden said. "At his age, and if he comes back, we have control of him for four years. It's worth the gamble to rehab him."
The Nationals would like to add more pitching at a cheap price, and that means they are out of the running to sign right-handers Tony Armas Jr., Tomo Ohka, Ramon Ortiz, Jorge Sosa or Steve Trachsel. In fact, according to a baseball source, Sosa is set to sign with the Mets.
In other news, the Nationals named Lee Kuntz as their head athletic trainer. He replaces Tim Abraham, who resigned last December during the Winter Meetings. Kuntz joins the Nationals after spending the previous four years as Cleveland's Minor League rehabilitation coordinator.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.