Campillo, who was with Soria on Mexico's team last spring, missed most of the 2009 season because of right shoulder tendinitis. He pitched in five games for Atlanta with a 1-0 record and 4.15 ERA.
Campillo, 31 and born in Tijuana, began his pro career with eight seasons with the Mexico City Tigers. His best year was 2003, when he was 12-5 in 21 starts and had a 2.79 ERA. He was acquired by the Mariners in 2005 and later that year underwent Tommy John reconstructive elbow surgery. In 2007, while pitching for Tacoma, he led the Pacific Coast League with a 3.07 ERA while going 9-6 as a starter.
Other players signed earlier this offseason to Minor League contracts by the Royals from outside the organization include infielder Wilson Betemit, catcher Edwin Bellorin and pitcher Brad Thompson.
The Royals also have re-signed or agreed to terms with several players who will return to the organization, including pitchers Kelvin Villa, Carlos Rivas, Jairo Cuevas, Juan Abreu and John Bannister, catchers Vance Wilson and Cody Clark, infielder Irving Falu and first baseman-outfielder Scott Thorman.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.