The move to sign Boyer continued a busy offseason for the Royals as earlier they acquired Wade Davis and James Shields from the Tampa Bay Rays in exchange for Wil Myers, Jake Odorizzi and Mike Montgomery.
Boyer last pitched in 2011 when he went 0-2 with one save and a 10.80 ERA in five games for the New York Mets.
Across seven seasons and 233 relief appearances, Boyer compiled a 4.81 ERA and had a 4-19 record. He gave up 17 home runs in 234 innings, struck out 162 and walked 94. His best asset in the majors has been his ability to get batters to put the ball in the dirt, as his ground ball rate is 55.6 percent according to Fangraphs.com.