Press release via mlb.com:
St. Pierre, 26, was selected by the Detroit Tigers in the 26th round of the 1997 First-Year Player Draft. He has played 10 seasons in the minor leagues for Detroit, batting .254 with 43 HR and 331 RBI in 762 games. St. Pierre was a Midwest League All-Star at Class-A West Michigan (2000), a Florida State League All-Star at Class-A Lakeland (2001-02) and an Eastern League All-Star at Double-A Erie (2003-05).
St. Pierre joined the Royals as a minor-league free agent on Jan. 24, 2007. He has been added to the roster at Triple-A Nashville.
Hendrickson, 26, was selected by the Brewers in the 10th round of the 1999 First-Year Player Draft. He went 1-10 with a 7.41 ERA in 14 games (12 starts) during Major League stints in 2004 and 2006.