King, who is considered a workhorse out of the bullpen, pitched for the Rockies last season. He appeared in 67 games and had a 4.43 ERA. King could join Micah Bowie as one of the lefties out of the bullpen for Washington. If King makes the Major League roster, he will earn $850,000.
King, 32, has played for five teams: Cubs, Brewers, Braves, Cardinals and Rockies. King said he signed with the Nationals because he is familiar with a few people in the organization, including team president Stan Kasten and general manager Jim Bowden, who drafted King in 1995 when he was with the Reds. King also befriended Nationals manager Manny Acta and catcher Brian Schneider during the All-Star Tour of Japan last November.
"Hopefully I could come in and get to where I need to be and pitch 70 to 80 [innings]," King said.
Asked why he didn't wait to make the big money like most of the free agents this offseason, King said, "We talked to a couple of teams and they gave me the impression that I didn't have a good year. As a player, you take that to heart a little bit. No. 1, I played at Coors Field. And you look at your track record -- I pitched in over 500 ballgames and had pretty good success.
"I like knowing where I'm going early. I could have rolled the dice and got something else. Who knows? I'm happy to compete for a job with the Nationals and, hopefully, help improve their ballclub."
Simontacchi, 33, hasn't played in the big leagues since 2004 with the Cardinals. That season he tore his right labrum. Simontacchi will compete for a spot in the Washington rotation.
His best season was in 2002, when he went 11-5 with 4.02 ERA for St. Louis.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.