Volstad was winless in 24 starts spanning two seasons with the Marlins and Cubs. Volstad got his first win of the 2012 season Aug. 26 against the Colorado Rockies and finished the season 3-12 with 61 strikeouts and a 6.31 ERA in 21 starts during the 2012 season.
In five seasons with the Marlins and Cubs, the 26-year-old right-hander is 35-51 with a 4.87 ERA and 439 strikeouts for his career.
Volstad spent time with Triple-A Iowa throughout the summer before being brought up by the Cubs for good Aug. 3 after they traded Ryan Dempster and Paul Maholm at the trade deadline.
The Royals' pitching staff ranked 23rd last year with a combined 4.30 ERA and a 72-90 record. The Cubs' pitching staff was ranked 24th with a 4.50 ERA